5271 Driver
NI-DAQmx installs support for NI Data Acquisition and Signal Conditioning devices. NI-DAQmx 14.5.1 addresses issues for USB DAQ devices, CompactDAQ controllers.
Download Acer Aspire 7730Z Suyin Camera Driver 5.2.7.1 for Windows 7 Digital Camera / Webcam / Camcorder.
- Can not find what you want.Click Here. Doc. Subject Date; CERT-13-0001072 CE EMC MIO-5271: 2013-12-30: CERT-13-0001073.
- Ford Escape Forums, Ford Escape Hybrid, 2013 Ford Escape Message Boards, Ford Escape Reviews, Mercury Mariner Forums, Mazda Tribute Forums, and Ford.
- Instead of a normal keyboard, the 5271 uses a 122-key keyboard with 24 function keys and various other 3270-specific keys. The keyboard plugs into a dongle, which in.
The most downloaded Audio Drivers software, including Realtek High Definition Audio Codec Windows Vista / Windows 7 / Windows 8 32-bit, Realtek AC 97 Driver.
Nov 02, 2012 PGA Golf Professional Andy Proudman Talks about the difference between playing an iron shot and a driver.
Nov 03, 2012 Mark Donovan of reviews the WORX SD SemiAutomatic Driver tool in this video.
The IBM 5271 can be briefly described as a cross between an XT model 5160
and a 3270 terminal. Indeed, the 5271 is also known as a 3270 PC.
The case, motherboard, hard and floppy drives, and power supply are all
identical or very similar to the XT. A specialised keyboard and display
both of which closely resemble the ones used by the IBM 3179 terminal replace
the XT equivalents. To support these, some or all of the following cards will
Keyboard controller. This also contains the BIOS for all the
special cards; so the video cards, for example, won t work without it.
Video card. I don t think it s got a name, other than
3270 PC Display Adapter - which, even abbreviated to 3270PCDA, is a
Host Connect card. Used to connect to the mainframe. The
connector is BNC like 10base2 Ethernet but isn t Ethernet.
One or two additional graphics cards see below.
With all these cards in the machine, that can leave as few as three
available ISA slots for the necessities such as hard/floppy drive controllers
It is possible to convert a 5271 to a normal XT, by removing the
specialised display and keyboard cards, and adding a normal display card.
Instead of a normal keyboard, the 5271 uses a 122-key keyboard with
24 function keys and various other 3270-specific keys. The keyboard plugs
into a dongle, which in turn connects both to the keyboard socket and to
The 5271 will work with a standard XT keyboard, but displays error 302
when booting; you have to press F1 to continue.
The manual describes two different models of keyboard controller: one
with an NMI button and serial port herein described as the complicated
controller, and one without herein described as the simple controller.
Both are illustrated. The manual also says that only the complicated
controller supports the use of the 3270 cursor keys in PC programs. Each
controller has its own ROM part no. 6323581 for the simple controller
and 6323582 for the complicated one.
Common to both types of controller is the custom chip that handles
keyboard signals: it appears to have the IBM part number 1503828, and the
Motorola part number SC81155P. Possibly it s a microcontroller, but I
don t know what type or if it is a microcontroller whether the contents
can be read without decapping.
The dongle or, as the Guide to Operations calls it, the keyboard adapter
cable is used to connect the keyboard to the keyboard card and the keyboard
card to the PC s normal keyboard socket. As far as I can tell, it contains no
electronics of its own; it s just there to split the DE9 socket on the
card into a couple of 5-pin DIN connectors.
When I bought my 5271, it was missing its proper dongle, but after copious
experimentation I was able to work out the pinout of the socket on the card,
and thence a suitable wiring diagram for the dongle. The pinout is:
To make the substitute dongle, pins 1, 2 and 9 should be connected to the
matching pins on the motherboard keyboard connector, and pins 4, 5, 6 and 9
to a 5-pin DIN socket for the terminal keyboard.
Pins 8 and 9 are both Ground, so it may make more sense to connect
Ground on the XT keyboard plug to pin 8 rather than 9.
Since the signals are compatible, it would also be possible to construct
a dongle that had a PS/2 socket, or a 5-pin AT socket, instead of a 5-pin
Disclaimer: While I have built a working dongle, it s
quite possible that I made a mistake when transcribing the diagram afterwards
or numbering the pins. It s a good idea to double-check your wiring against
as many references as you can find before actually plugging the thing in
On the left: an original IBM Keyboard Adapter Cable. On the right: my
img src width 600 alt The two dongles,
The keyboard appears to use I/O ports 01B0h to 01B7h. It can raise
If the 3270 scancode 5 SysRQ is received, port 0189h is read. The
top bit is flipped and the value written back out again.
Send keyboard controller command. This appears to be a bitmap,
since all the commands are powers of 2. They include:
00hNormal operation. After this command, the
keyboard status can be read from port 01B2h.
08hSet XT keyboard clock. When the firmware simulates
an XT keypress, it writes the scancode to port 01B1h and
then sends 08h followed by 00h to this port.
10hSend a command to the keyboard cf writing to port 60h
on an AT-class machine. Command bytes are written to
port 01B1h; then 10h is sent to port 01B0h, and the
keyboard status is read up to 80 times until bit 5
goes high. If bit 5 doesn t go high, keyboard
initialisation is deemed to have failed.
Commands sent during initialisation are:
Set defaults and disable keyboard.
Set some keys to generate break codes. This
is done for keys 9, 77h, 7Eh, 65h CTRL, NumLock,
Set some keys to repeat and only generate make codes.
Corresponds to command FBh on a PS/2 keyboard, and is
followed by a list of keycodes. The keys it is applied to
are the numeric keypad keys, the function keys, and DEL.
20hRead scancode from keyboard. The scancode can then be
40hUsed in initialisation. 24h is written to the XT
scancode port 01B1h. Then the keyboard status is
read until bits 6 and 7 go high, which appears to be when a
80hUsed to acknowledge a keystroke. In the IRQ2 handler,
the keyboard status is read. If the low bit is 1, then
80h is written to port 01B0h, followed by 0.
Output XT scancodes to this port to send them into the normal
keyboard connector. After sending a scancode, send 08h and then
Data register. Value read depends on last value written to port 01B0h.
The registers belonging to the 8254 timer on this board.
They get initialised to preset values at startup, and are not
Counter 0 generates a square wave with period 4 possibly a basis for
the keyboard clock signals, or perhaps a clock for the microcontroller
itself ; counters 1 and 2 are set up in software triggered mode with
The following variables are used in the BIOS data segment:
Bit 0 is 1 if the standard keymap is in use, 0 if a custom
keymap has been loaded by INT 52h. It s possible to load two
custom keymaps by loading the first, setting this bit, and then
loading the second. Note that on AT and later computers, this bit
is set if the left ALT key is down.
Segment of current scancode translation table. The
complicated controller stores this at C010.
Segment of alternative scancode translation table.
Loading a custom map with INT 52h sets this to the previous default table.
Using CTRL ALT F1 or CTRL ALT F2 to select keymaps swaps the two
table pointers over if necessary. The complicated controller
Last translated XT scancode. The complicated
controller stores this at C014.
Last 3270 scancode received. The complicated controller
The keyboard, and its scancodes, now have their
The 5271 video hardware is composed of between one and three full-length
ISA cards. If multiple cards are present, they are connected together using
Implements 25x80 text mode, and provides video output.
Implements CGA graphics modes, plus two modes unique to the 5271.
Allows a user-defined character set to be loaded only used by 3270
The video switches on the motherboard need to be configured as
EGA/VGA rather than MDA or CGA. Depending on what hardware is present,
the video BIOS will adjust the settings to behave as MDA or CGA. For
some reason the video BIOS is a located in the ROM
on the keyboard controller card; and b mapped into memory in two
The simple keyboard controller maps its onboard ROM into memory in two
C0000-C07FF: The first 2048 bytes of the ROM: Video self-test
CA000-CA9FF: The remainder of the ROM: Mode changes, the display
configuration table, and the keyboard.
The complicated controller does something more like this:
C0000-C01FF: The first 512 bytes of the ROM: Self-test of ROM checksum and
C0400-C05FF: RAM, used to hold controller state.
CA000-CA3FF: The last 1k of the ROM: the code that has to stay paged at
all times. Interrupt handlers, helper routines.
CB000-CBBFF: Bank-switching window in which any part of the ROM can be mapped,
based on the value written to port 12D8h.
The video card behaves rather like a 3270 terminal screen in front of
a CGA or MDA screen. At startup, the 3270 screen is transparent and can t be
seen; a terminal emulator program would make it visible.
I don t have a complete pinout for the monitor socket. It s DE9, with
at least the following pin assignments:
Pins 6,7,8: On a colour monitor these are the three colour signals; I m
not sure what order they re in.
On a mono monitor, pin 6 is intensity probably blue,
pin 7 is video probably red, and pin 8 is horizontal
Pin 9: On a mono monitor, pin 9 is vertical sync.
Most of this information comes from studying the boot ROM, the diagnostic
utility INDLTDUK.DGS and the driver for the 3270 client software
From 0A0000h to 0A1FFFh is the 3270 s frame buffer. This appears to have
Byte 0: Character. 0FFh for transparent cell, so the CGA or
MDA screen shows through. The other values correspond to characters
not ASCII and not EBCDIC; this is the 3270 internal character set.
Byte 1: Attribute. On a colour display:
Bits 0-2: Background colour. 0 Black 1 Blue 2 Red 3 Pink 4 Green
Bits 3-5: Foreground colour. 5 Cyan 6 Yellow 7 White
Bits 6-7: Attribute: 0 Normal 1 Blink 2 Inverse 3 Underline
Ignored for Programmed Symbol fonts 4,5,7 when drawn in
white on black; see Tri-plane fonts below.
Bit 5: Foreground: 0 Normal 1 Bright
Byte 2: If the Programmed Symbols board is not present, this
byte cannot be written, and when read is either 0FFh or 0FEh.
If the board is present, then the bottom 3 bits select the symbol
set to use; 0 for the ROM font, 1-7 for the seven RAM fonts.
Byte 3: Cannot be written; when read, it is always 0FFh or 0FEh.
AE000-AFFFF: Programmed symbols memory
If bit 3 of port 0188h is set, the initialisation code will test 8k of
memory from AE000h to AFFFFh. This holds the RAM font for programmed symbols
see above. The shape data for each character is 16 little-endian words long,
with bits 15-7 of the word giving the character shape; bits 6-0 are always
According to its box, the PSS board can hold up to 7 fonts. Internally,
it has storage for 1536 characters, which can be used either as six
256-character fonts, or three 256-character fonts plus four 192-character
fonts. The low 3 bits of port 0195h select which font is mapped into memory
Font 6 shares its memory with the last 64 characters of fonts 1-3:
Font 6 chars 00-3F Font 1 chars C0-FF
Font 6 chars 40-3F Font 2 chars C0-FF
Font 6 chars 80-3F Font 3 chars C0-FF
Font 6 chars C0-FF always blank
Thus, these memory ranges can either be treated as four 192-character
fonts using the first 192 characters of fonts 1,2,3 and 6 or as three
256-character fonts using all of fonts 1,2 and 3.
The Programmed Symbols board holds the fonts 4, 5 and 7 as three separate
planes red, green and blue. Bits 3-5 of port 0195h select which plane s are
written at AE000h. The practical effect is that characters in these fonts
are held, and can be displayed, as an 8-colour bitmap.
For a tri-plane font, the value read from memory at AE000h is the bitwise
OR of the planes selected by port 0195h.
When the characters are drawn onscreen, they appear in 8 colours only for
the four attributes 38h, 78h, B8h and F8h in other words, when drawn in
white on black. The blink, inverse and underline attributes have no
effect when characters are drawn in 8 colours. On a monochrome display, the
red plane is mapped to video, and the blue plane to intensity.
For all other attributes, the character shape drawn is the bitwise OR of
By way of demonstration, here s what can be done with the aid of tri-plane
This is actually mapped to the same memory as the CGA framebuffer; changes
to one will affect the other. The buffer is 4k in size, so it repeats at
B8000-BFFFF: CGA and APA memory
The main video card actually only has 8k of memory on it - 4k for the
3270 display, and 4k for the MDA/CGA display. So the CGA display RAM repeats
at B9000h, BA000h etc in text modes; the APA board takes over in graphics
modes. This means that applications that try to use multiple CGA pages won t
If bit 2 of port 0188h is set, the initialisation code will test 32k
of memory from 0B8000h to 0BFFFFh. Otherwise it just tests from 0B8000h to
On a colour display, the following attribute system is used for both CGA
Bits 0-2: Foreground colour, matching IBM CGA.
0 Black 1 Blue 2 Green 3 Cyan 4 Red 5 Pink 6 Yellow 7 White
Bit 7: Blink if blinking is enabled.
The I/O ports used by the video card include:
Output writes to current CRTC register, and increases pointer by 1. So, for
example, if the current CRTC register is 6 and a byte is written, register
6 will be updated and the next write will be to register 7.
Command register. Commands include:
00hSent four times at start of initialisation sequence.
Select CRTC register to be written at port 0180h.
Register number is passed in the low nibble of the command.
CRTC registers and their default values are:
006868Bits 7-3: Character height - 1
Bits 2-0. something to do with
011E18A horizontal timing value, possibly
049898Bit 7: Zero for fast blink.
06DDDDCursor shape: high nibble top row,
if set, you should halve the rows displayed value
09F0F0Appears to be some kind of mask and/or
increment applied to the top 4 bits of the CRTC s source address. When high
4 bits are 0, low 4 bits appear to be an increment:
00 Next address displayed after 03FF is 0000
01 Next address displayed after 03FF is 0100
02 Next address displayed after 03FF is 0200
03 Next address displayed after 03FF is 0300
04 Next address displayed after 03FF is 0400
05 Next address displayed after 03FF is 0500
Possibly the high 4 bits are the mask and the low 4 the increment.
3ChDisable video output and turn cursor off ie, if
video output is enabled with 2Dh, cursor will be off.
3DhEnable video and turn cursor on.
48hClear line 0 latch see below.
50hClear vertical blank latch.
58hClear line 0 latch and vertical blank latch.
The byte read from port 0181h which the diagnostic program calls 2672
Bit 4: Vertical blank latch. Set by vertical blanking interval; cleared by
Bit 3: Line 0 latch. Set by screen line 0 being drawn; cleared by command 48h.
Start screen address. These two bytes should be treated as a
14-bit value the low 8 bits at 0182h, the high 6 bits at 0183h. They
set the first character to display for both 3270 and CGA/MDA
framebuffers. The address is in characters rather than bytes; to
put line 1 at the top, set the address to 80 50h.
Cursor location. Held in the same way as start screen address.
0188hRead-only register: Hardware status.
Bit 6: Diagnostic readback, red. See 0189h below.
Bit 5: Diagnostic readback, blue.
Bit 4: Diagnostic readback, green.
Bit 3: Set if Programmed Symbols board is present.
Bit 2: Set if All Points Addressable board is present.
Bit 1: Set if a monitor is present.
Bit 0: Monitor type - 1 5272 colour, 0 MDA mono.
A read/write register. The self-test checks this by storing 0FFh
and 0 in it, and checking that it can read back both values.
The bits used in this register are:
Bit 7: Toggled when SysRQ is pressed.
Bit 6: In normal use, initialised to 1 by the BIOS.
Bit 5: Enable diagnostic readback on bits 6-4 of port 0188h.
Bits 3-0: CGA/MDA framebuffer offset, high 4 bits see 018Ah below.
The diagnostic readback is used by the self-test. When it is turned on,
the red/green/blue bits in port 0188h go high and stay high when anything,
including the cursor, is drawn in the corresponding colour. So the self-test
checks firstly that blank video RAM causes nothing to be drawn, and then that
a pattern in video RAM causes something to be drawn.
If the system has a mono monitor, only the red and blue output
lines presumably some combination of video and intensity appear
018Ah, together with the low 4 bits of 0189h, are referred to by
the diagnostic program as PC offset. They hold a 12-bit value
018Ah gives the low 8 bits, 0189h the high 4. The values read from
these ports give the offset currently in use, which may not be the
same as the value written to them.
This value is used as the index, in the MDA framebuffer, of the
character to display at 0,0. Port 018Bh is initialised by the
BIOS to 90h, which resets the low 4 bits of 0189h and all of
The values written to port 018Bh appear to act as commands.
If the top bit is not set, then the low nibble seems to indicate a
x0h clears bit 0 of port 018Ah
x2h clears bit 1 of port 018Ah
Port 018Ah is also used by the diagnostic diskette to detect
3270PC hardware; it writes 0 to this port and checks that the value
Interrupt/Control register. Set bit 6 of this port to enable
interrupts on IRQ2, triggered when a value is written to an emulated
CGA register. Other bits are always written as 0.
The diagnostic diskette tests that bits 6 and 0 of this port can
hold the values written to them.
On read, bit 4 is set if interrupt was triggered by a write to the
CGA mode control register port 03D8h ; bit 5 if it was triggered by a
write to the CGA cursor position 6845 registers 0Eh/0Fh or cursor
A counter which appears to affect the vertical position of the video
output on the screen. Written to by the ROM and the diagnostic diskette, when
reinitialising the adapter. In each case, two bytes are written, forming a
little-endian word. For mono, the value is 88A9h; for colour, 9569h.
When read, returns the current value of the counter, working down from
the maximum value written to 0.
Left margin. Written to by diagnostic diskette, when reinitialising the
adapter. As 0190h, a little-endian word; values written are
0060h mono, 0065h colour and 0061h during tests. The higher the value,
the further to the left the screen is drawn.
This appears to be another little-endian word. The ROM initialises it to
0050h, and then leaves it alone. Writing other values does not appear to have
any effect. On read, the result is always 0.
Written to by the ROM and the diagnostic diskette, when reinitialising
the adapter. The only values written appear to be 32h immediately before a
write to port 190h, 72h after writing to port 190h, and at other points in
the diagnostics, 0BAh final initialisation in ROM.
Read by the diagnostic program. Always appears to return 0FFh.
Programmed Symbols Mask register.
Bits 0-2: Select font memory bank at 0AE000h, number 1-7.
Bit 3: Write blue plane on a mono monitor, intensity
Bit 5: Write red plane on a mono monitor, video
The selection of planes applies to fonts 4, 5 and 7; these fonts are held
as three planes, allowing characters to have an intrinsic colour. If all of
bits 3,4 and 5 are zero, all three planes are written as if they were all 1.
Font 6 shares memory with the last 64 characters of fonts 1,2,3.
All Points Addressable registers.
Mode select for 720 350 or 360 350 mode is:
For all other modes text and CGA-compatible graphics, it is:
The initialisation code sends:
The diagnostic program calls this Video Ctl Reg. When written
Bit 4: Odd pixel flag. The register at 0197h shifts the graphics bitmap
pattern to the left in units of 2 pixels. This setting shifts the
pattern one pixel to the right, allowing exact positioning of the
graphics viewport within the screen. This flag should only be used
in the 1bpp graphics modes 720 350 and 640 200 ; in the
2bpp modes, it takes effect before the bit stream is converted into
colours. So, for example, the bit pattern 10110000 magenta, white,
black, black would be shifted to 01011000 and then interpreted as
Bit 3: Select mode. Set for native mode linear framebuffer of 31500 bytes.
Clear for CGA-compatible mode interleaved framebuffer of 16192 bytes.
Bits 2-0: Appear to be connected to the diagnostic readback on the low 3
bits of port 0197h possibly a bitmask.
Referred to by the diagnostic utility as Pell sic Offset Register. When
written, causes the graphics screen to be shifted to the left at the pixel
7F 01111111 Bytes are displayed unshifted
BF 10111111 Screen is shifted left by 2 pixels 1 pixel in 360 350 and 320 200 mode
DF 11011111 Screen is shifted left by 4 pixels 2 pixels in 360 350 and 320 200 modes
EF 11101111 Screen is shifted left by 6 pixels 3 pixels in 360 350 and 320 200 modes
F7 11110111 Screen is shifted left by 8 pixels 4 pixels in 360 350 and 320 200 modes
FB 11111011 Screen is shifted left by 10 pixels 5 pixels in 360 350 and 320 200 modes
FD 11111101 Screen is shifted left by 12 pixels 6 pixels in 360 350 and 320 200 modes
FE 11111110 Screen is shifted left by 14 pixels 7 pixels in 360 350 and 320 200 modes
FF 11111111 Entire CGA/MDA screen displays in solid white.
Other values have unpredictable results. For example 3Fh 00111111b shifts to
the left by one pixel and masks each byte with itself shifted by one bit
so 2-pixel uprights in letters become 1-pixel.
Bit 7: Always 0. At least, the APA self-test and the diagnostic diskette
Bit 3: Reflects bit 3 of value written to port 0196h.
Bits 2-0: Used when testing the CGA colour select register; in the diagnostic
utility, the value read from these bits should reflect the value
written to the colour select register. At a guess, they re the colour
of the pixel currently being drawn, at least during that particular
When testing this port, the diagnostic diskette writes the values 1,2,4,8
to port 0196h, and checks that the corresponding value read from port 0197h
The diagnostic program calls this Start offset counter. Two successive
bytes are written to it, forming a little-endian word, giving the number of
blank words to output before beginning to draw the contents of the graphical
For some reason, the value 0000h places the graphics origin 5 words to the
right of the top left-hand corner of the screen. To get at the first four
words of the screen, 3D82h-3D85h are used.
In CGA graphics modes, this word is initialised to 0C7Ah. In the native
graphics mode, it is initialised to 3D82h.
The current value of this counter can be read back by two successive
reads from port 0198h for the low and high bytes. Depending what part of
the screen is being drawn, it can return anything from 0 to the value
The diagnostic program calls this Display Width Counter. Initialised
to 2Ch by startup, and not subsequently touched.
The value in this register, less the value of the Graphics Width Counter
019Ah gives the number of blank words output between each line of the
graphical framebuffer. If it is set to 59h 89 rather than its usual 2Ch 44,
then 45 blank words ie, a blank line will be output between each line of
Decreasing this below the value of the Graphics Width Counter has
When read, returns the current value of the counter ie, anything from 0
The diagnostic program calls this Graphics width counter. It holds
the number of 16-bit words on each line of the graphical display less 1.
Zero, and values above 2Ch, are treated as 2Ch.
The APA card always draws a fixed number of bytes from the framebuffer, so
halving the width of the graphics area doubles its height.
Various values are written at initialisation, but not subsequently. The
meaning of the values is not generally known, but:
3Ah appears to be written before an attempt to write to port 0198h. Possibly
this resets the flip-flop on that port, so that the next read/write is
guaranteed to access the low byte of the value.
5Ah is written before a write to port 199h.
9Ah is written before a write to port 19Ah.
At least some of the emulated CRTC. The IRQ2 handler reads
registers 0Eh/0Fh cursor location and 0Ah/0Bh cursor size ; on a
real MDA/CGA, the latter two cannot be read.
CGA mode control register. Read/Write in the 3270 PC, because at least
some CGA emulation is done by the firmware.
Simulated MDA / CGA status register. Alternate reads of these ports
Used by the complicated keyboard controller card. It appears to set
which range of the ROM is visible in a memory window from 0CB000h to
The monitor model 5272 is bigger than a normal CGA or MDA monitor,
and has a swivelling/tilting stand. It is capable of Hercules resolution
720 350 in 7 colours plus black.
A standard MDA monitor can also be used on a 5271. The graphics card
detects whether the monitor is colour or mono, and restricts the available
The font used in the 5271 uses a 9x14 character cell, the same as the
MDA. However the font has been changed from serif to sans-serif, and looks
markedly better as a result. In addition, other characters than those in
the range 192-223 make use of the 9th pixel column - for instance, the q
The font used for the 3270 terminal framebuffer at 0A0000h
uses a 3270 native encoding, which is similar to the 3270 CG encoding
but diverges quite a bit in the last 64 characters.
The fonts are stored in two 8k ROMs on the display board. One ROM holds
the left-hand 8 pixels of each character; the other just holds the ninth pixel.
In text mode, the 5271 behaves something like a CGA. However, there is
no high intensity; high intensity and standard colours look exactly the
same. The actual colours look quite different, too.
The following palette values are approximate. The normal ones come from
Linux DOSEMU; the 5271 ones from putting a VGA beside the 5271, and fiddling
with the VGA palette until the two displays looked similar.
ColourIBM 5271 colourNormal colour
The table suggests that the 5271 uses 4 possible levels for each of the
three primary colours roughly, 30, 80, A0 and C0. I suspect that these
colours are generated in the monitor, with the host PC sending simple on/off
Starting at the hardware level: The hardware of the CGA controller is not
emulated completely, only enough to support a standard CGA BIOS. The CGA mode
control register at 03D8h differs in the following respects:
The register is read/write, not write-only.
In text mode, bits 0 40x25 mode and 3 enable/disable display are
ignored completely. Attempts to select a 40x25 mode will be caught by
the IRQ2 handler and converted to the corresponding 80x25 mode.
In graphics modes, changing any bit of this register except bit 1 will
cause the video RAM to be cleared by the IRQ2 handler. This means that you
can t switch between the Red/Cyan/White CGA colour scheme and the other two
Red/Green/Yellow or Magenta/Cyan/White without a full mode change.
In addition, most of the 6845 CRTC is not emulated; so it is not
possible to select the 160x100 graphics mode by starting in 24x80 and
Although the 5271 s graphics card provides its own video BIOS, this does
not replace the standard ROM BIOS. The ROM is still used for nearly all
functions, the exceptions being function 00h set mode and 30h locate
This does a little extra hardware setup, stores the correct aspect
ratio for the selected mode, and then jumps to the ROM BIOS routine.
It also supports two extra modes, numbers 30h 720 350 mono graphics
and 31h 360 350 4-colour graphics, using CGA palette.
Function 30h CX 0 : Return 3270 PC configuration table
The 6323581 ROM does not check CX. The 6323582 ROM requires CL to be
zero, but does not care about CH.
The table returned CX:DX points to it is similar to that described
in the Interrupt List, but it is at most 6 bytes long, and possibly as few
02h: Monitor type 0 MDA or 5272.
04h: Video adaptor type 0 standard 5271, 1 XGA, 2 G/GX.
Present in the 6323582 ROM only. CH is a translated code passed from
the keyboard table. CH 0D9h is treated as SysRQ: if ALT is pressed, toggles
the top bit of port 0189h, else beep. CH 0FDh always beeps; other values of
In the 6323582 ROM, calling this function with CL 2 or higher will
return leaving CX unchanged and Carry clear.
The two extra graphics modes have a very simple memory layout - simply 350
lines of 90 bytes each, with no interleaving or funny tricks.
The following addresses in the BIOS data segment are used by the 5271
00C8: Aspect ratio X start of 3270PC configuration table
00D8: BIOS INT 10h handler address.
00EE: Result of self-test bitmap. 0 if all tests passed; bits set
3202Programmed Symbols card fault
3203All Points Addressable card fault
There are two types of card supported by IBM s diagnostic program - an
older model long card adapter, and a newer one. The 5271 s
ROM only detects the older model; this has a 4k buffer at 0CE000h and
uses I/O ports from 2D0h to 2D6h. The newer version adds a port at 2D7h
which seems to be used to set the base address of the buffer, increases
the size of the buffer, and makes the I/O port base configurable using
switches on the card. A BIOS upgrade to support the new shorter cards
The technical reference for the older version of the card can be found
02D0 Interrupt / Status register. Bits 0-5 interrupt reason set by card,
Bit 2 Visual / Sound Register Updated
Bit 4 Base Buffer Modified Complete
Bit 5 Load I/O Address Command Decoded
02D1 Visual / Sound Register. On read:
Bit 1 Inhibit Feature Step of Address Counter
02D2 Cursor Address Register bits 7-0
02D3 Cursor Address Register bits 15-8
02D4 Control Register. Read/Write:
Bit 3 Key pressed set by PC after Scan Code Register loaded; reset
by card when scancode transmitted.
Bit 7 Disable interrupts from card to PC
02D5 Scan Code. Written by PC to send a scancode to the host.
02D6 Terminal ID. Must be set before enabling the link.
2801Host Connect card initialisation failed
The 5271 was the first in a line of PCs with hardware support for 3270
terminal emulation. Information about later such PCs is extremely sketchy;
The 3270 PC/G and 3270 PC/GX. These added more sophisticated
graphics capabilities and mouse support. A different monitor
model 5279 or 5379 is used. According to this
USENET thread, the 5279 monitor has a separate tilt/swivel base 5278 packed with
circuitry and connected by a connector that s at least 75 way.
Similarly the 5379 a 19 monitor uses a
The 3270 AT, 3270 AT/G and 3270 AT/GX - the same sort of
specialist cards, but hosted in an AT rather than an XT.
gives the following display-card-and-monitor combinations:
13295 plasma display A large plasma
display that could show one, two or four 3270
25151 or 5272 with XGA Unknown
3270 PC/GX or 3270 AT/GX. Possibly C stands for
: XGA appears to be one of those reused abbreviations that causes endless
confusion. According to the 3270 Workstation Program Users Guide and
Reference, it refers to an Expanded Graphics Adapter Card that seems
to have disappeared without a trace. The acronym was reused by IBM in 1990 for
their Extended Graphics Array, and that s its general meaning
By the time of the PS/2 era, 102-key keyboards and VGA graphics meant
that there was no need for specialised hardware, and later 3270 emulation
appears to have been done with just software and a Host Connect card.
nothingtodo.org has a picture of a 5271 with its proper keyboard.
yesterpc.com has a large number of pictures of the AT version
of the 3270PCDA. This differs in various respects from mine; for
example, the video BIOS appears to be in a separate chip on the All
Points Addressable board rather than being part of the keyboard
controller, and both the APA and Programmed Symbols boards are of
a shape to fit in a 16-bit ISA slot.
Bitsavers have a number of 3270PC manuals.
The following patents mainly seem to describe the windowing system on
Recently the motherboard in my 5271 failed with a blown capacitor, and
while I had the PC dismantled pending repairs I experimented with putting
the video card in a couple of other XTs to see what would happen. After a
bit of fiddling, I was able to get it to work on both systems I tried: a
Sinclair PC200, and an Amstrad PC3086. Based on this small sample size,
here is my advice for using 5271 hardware on other systems:
If your XT has any sort of built-in video subsystem, it must be
The video cards will only fit in full-length 8-bit ISA
slots. I haven t experimented with AT motherboards, but even for
a simple test you d need one with an 8-bit ISA slot. For the full
trio of video cards you need three adjacent 8-bit slots at the
The minimum requirement is two slots, one full-length; the
full-length slot for the video card, and the other one for the
keyboard controller with the ROM.
The maximum requirement is five slots - the above cards plus
the All Points Addressable, Programmed Symbols and Host Connect
Morocco chauffeur services offer Morocco airport transfers in Marrakech Casablanca Tangier,budget car hire Minivan tours with English speaking driver.
