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└─⟦a0efdde77⟧ Bits:30001252 EUUGD11 Tape, 1987 Spring Conference Helsinki
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.\"$Header: ibmaed.4,v 10.1 86/11/19 10:55:57 jg Exp $
.\"$Source: /u1/X/libibm/doc/man/RCS/ibmaed.4,v $
.\ This file uses -man macros.
.TH IBMAED 4 "31 Mar 1986" "Space overwritten by .AC macro" " "
.UC 4
.AC 1 0
.SH NAME
ibmaed, aed \- IBM Academic Information Systems experimental display interface
.SH SYNOPSIS
.B "pseudo-device aed"
.SH DESCRIPTION
The IBM Academic Information Systems 
experimental display is a black-and-white,
all-points-addressable, bit-mapped display with 812,900
points on the screen.
It is driven by an adapter with an on-board processor.
The processor executes a microprogram loaded by the host
into the display's control store.
The microprogram controls the 
interface between host and display.
The host communicates with the microprogram
through an area of read/write shared RAM.  This memory 
starts at address 0xf40a4000 and is organized as 4K 
of 8-bit bytes.
.PP
On system startup, the display driver loads the control store
with a default microprogram that is part of the driver's initialized
data area.
The display operates in glass tty mode (the default)
and window-manager mode:
.IP -
In glass tty mode, the display serves
as the default display device for \fI/dev/console\fR.
Kernel printfs and characters written to \fI/dev/console\fR 
are written to this display.
Default mode is in effect when the microprogram starts.
.IP -
In window-manager mode, a user-level process,
such as a window manager, can load its own microprogram
into the display's control store, and read or write to 
the display's communications memory.
When a process opens \fI/dev/aed\fR, the kernel switches
console output to another display device, if available, or buffers the
output until later (see 
.IR cons (4)). 
At this point,
the control memory and communications memory 
are available for manipulation by the user process.
Glass tty mode is reentered when \fI/dev/aed\fR is closed.
.PP
The following system calls are supported by \fI/dev/aed\fR:
.ft B
.IP "open" 8
.ft R
Initiates window-manager mode.
Only one process can open \fI/dev/aed\fR.
All file descriptors must be closed before another open is allowed.
The process and its children that have file descriptors open
to \fI/dev/aed\fR have direct access to the display's shared RAM, until an
.IR execve (2)
system call is completed.
.ft B
.IP "close"
.ft R
Terminates a process's read/write access to the display's 
shared RAM.
The last close to \fI/dev/aed\fR ends window-manager mode and reinstates
glass tty mode.
.ft B
.IP "read"
.ft R
Allows read access to the display's control store.
.ft B
.IP "write"
.ft R
Allows write access to the display's control store.
.ft B
.IP "ioctl"
.ft R
(Ioctl's defined in <\fIsys/aedioctl.h\fR>)  AEDSEM_WHILE,
AEDSEM_UNTIL, AEDSEM_SET_WAIT all poll the semaphore, 
waiting for   
an event. A specified number of polls occurs before the call returns
with a failing (-1) return code.  You may alter the default of 250 polls by
issuing a AEDSEM_TIMEOUT request.  It is often advisable to reissue the failed
call later, allowing the display a little more time.  It is up to
the programmer to decide how many tries make sense before the display can be
assumed to be hung.
The following requests are supported:
.IP
IOCINFO	Returns device information.
.IP
IOCTYPE	Returns device type.
.IP
AEDGET_SRAM_LOC	Reports address of display-shared RAM.
.IP
AEDRESET	Resets the display. The display processor is
.br
		halted and the program counter is set to 0.
.IP
AEDSEM_READ	Reads the display semaphore.
.IP
AEDSEM_SET	Sets display semaphore to a specified value.
.IP
AEDSEM_SET_WAIT	Sets display semaphore to a specified value and waits
.br
		for it to change, then returns the new value.
.IP
AEDSEM_WHILE	Polls display semaphore until it is no longer equal to
.br
		a specified value.
.IP
AEDSEM_UNTIL	Polls display semaphore until it is equal to a specified 
.br
		value.
.IP
AEDSEM_TIMEOUT	Sets the timeout interval.  The default is 250 polls.
.br
		See AEDSEM_WHILE, AEDSEM_UNTIL, AEDSEM_SET_WAIT.
.br
		A request to set the timeout to zero returns the current
.br
		timeou