
already installed at particular addresses. There are several ways
round this. Firstly, try running the board at address 180H(see
Section 3 for installation information). This is often unused. If you
can't get any information from the PC manufacturer, run a program
like Quarterdeck's Manifest, which makes a reasonable attempt to
discover the addresses of common peripherals. Finally, see Section
3 for fault-finding information.
The Registers on the PCSYSCON
The following table shows the I/O registers on the PCSYSCON.
The following table shows the special function registers on the
PCSYSCON.
How to Write to the Registers
It is useful to remember that the pointer register only needs to be
written to once if only one register is read or written. This means that
I/O can then be done with byte reads and writes. However, if your
program is continually changing registers it must write a new pointer
value each times it accesses a new register. This can be done by
writing a pair of bytes as a word, because the CPU in a PC does
word writes to the bus (which is one byte wide) by writing the lower
byte first, thus setting up the pointer register first.The sub-section A
Quick Installation Test shows the basics of how to write to the control
register.
2192-09065-000-000
Section 2. The PCSYSCON I/O Map
Page 10
J278 PCSYSCON
Pointer Value
09
08
08
07
06
05
04
04
03
02
01
00
STARTW
STATUS
RETRIGW
BUZM
RELM
INTM
G1IN
G0OUT
DACTEMP
DAC-12
DAC+12
DAC+5
W
R
W
R/W
R/W
R/W
R
W
R/W
R/W
R/W
R/W
Start watchdog and set final timeout
Read board status
Retrigger watchdog
Buzzer mask
Relay mask
Interrupt mask
Read from group 1 inputs
Write to group 0 inputs
Set temperature comparison
Set -12V comparison
Set +12V comparison
Set +5V comparison
Register Name Read/write
Comments
Pointer Value
81H
Board Ident
User LED
R
W
Reading this should always give a value of 80H
for the PCSYSCON
Writing 01 switches the green LED on. Writing 00
switches it off.
80H
Register Name Read/write
Comments