NAME

ibm6155, apa16 − IBM 6155 Extended Monochrome Graphics Display interface

SYNOPSIS

pseudo-device apasixteen

DESCRIPTION

The IBM 6155 Extended Monochrome Graphics Display is a 15-inch CRT with gray-white phosphor, driven at 60 Hz non-interlaced.  It provides a monochrome, all-points-addressable, bit-mapped display with 786,432 points on the screen (1024 pixels on each of 768 displayable lines).  All pixels are directly accessible by the workstation’s CPU.  A fast raster-operation processor is provided with built-in capability for bit-block transfer, line draw, image copy/merge and image rotate. A graphics queue mechanism with synchronization and controlled branching allows pre-programmed graphics subroutines. A 48x64-bit hardware cursor provides instant cursor operations without disruption of display data. 

The display adapter is a single PC/AT card installed in the I/O bus as a sixteen-bit device. The display appears to the system as two separate memory areas: a 128k block of system memory, and 20 bytes of I/O space (addressed from 0xd10 through 0xd2f, and 0x6f3).  The 128k block defines both the visible frame buffer (addressed from 0xf4d80000 through 0xf4d97ffe) and the hidden, off-screen memory area (addressed from 0xf4d98000 through 0xf4d9fffe). The 20 bytes of I/O space access the display adapter’s control registers. 

The display operates as /dev/ttyap16 in glass tty (the default) mode and /dev/apa16 in window-manager mode:

-Glass tty mode initialization consists of the downloading of a character font and certain graphics subroutines into the adapter card, followed by a cursor home and screen clear.  In this mode, the display driver emulates a smart terminal, similar to an IBM 3101, and can be /dev/console.

-In window-manager mode, a user-level process, such as a window manager, can directly control the display device hardware, loading control programs, accessing display buffers, etc.  When a process opens  /dev/apa16, output intended for /dev/ttyap16 is buffered by the kernel until later (see bufemul(4)).  The process must then open /dev/bus to access the display control memory areas for manipulation by the user program if bit 0x8 is not set in the minor device number.  Glass tty mode is reentered when /dev/apa16 is closed. 

DIAGNOSTICS

None. 

ERRORS

The following errors can be returned by the interface:

[ENODEV] Nonexistent display (on open, close, read, write, or ioctl);
Unavailable display (on open):  user processes are denied access to this display (see consoles(5), setscreen(8)).

[EIO] Made an attempt to close a display device that was not open. 

[EBUSY] The display has already been opened by a user process. 

NOTES

Ibm6155 is not supported on the IBM 6152 Academic System. 

FILES

/dev/apa16
/dev/ttyap16
/dev/console

SEE ALSO

bufemul(4), bus(4), cons(4), ibm5081(4), ibm5151(4), ibm5154(4), ibm6153(4), ibm6154(4), ibm8514(4), ibmaed(4), ibmemul(4), kbdemul(4), tty(4), vga(4)
“IBM/4.3 Console Emulators” in Volume II, Supplementary Documents

BUGS

Access to the PC/AT I/O and memory busses through /dev/apa16, when bit 0x8 is set in the minor device number, is not limited to the apa16 addresses. 
 

PRPQs 5799-WZQ/5799-PFF: IBM/4.3  —  July 1987