NorthStar HORIZON Manual page 78

a. the data bits to the printer
b. the output done signal from the printer to the ACK/
signal at the connector
c. the SPARE/ signal from the connector to the printer
strobe signal.
The following assembly language subroutine will output the value
1n the B-register to the printer and then return.
POUT IN 6
ANI 1
JZ POUT
MOV A,B
OUT 0
MVI A,20H
OUT 6
RET
PARALLEL INPUT EXAMPLE
READ MOTHERBOARD STATUS
MASK TO GET PO FLAG
PRINTER NOT YET READY
RESTORE DATA TO A-REGISTER
OUTPUT DATA TO PRINTER
LOAD COMMAND BYTE TO A-REGISTER
RESET PO FLAG
To configure for input from a parallel keyboard:
A. Connect pin 6 to pin 9 if the positive-going edge of the
input strobe signal from the keyboard should set the P-I-FLG
flip-flop. (Connect pin 7 to pin 9 if a negative-going edge
should set the flip-flop.)
,
B. Construct a cable from the keyboard to the IS-pin Parallel
Input Connector which connects the data bits from the
keyboard to the corresponding data bits at the connector and
which connects the strobe signal from the keyboard to the
input strobe pin at the connector. It is possible to supply
power to the keyboard from the motherboard by cutting traces
and wiring power to pin 13, 14, or IS of the connector.
The following assemblY,language subroutine will input a character
from the keyboard and return with the character value in the A-
register.
PIN
IN
6
ANI 2
JZ PIN
IN 0
PUSH PSW
MVI A,30H
OUT 6
POP PSW
ANI 7FH
RET
READ MOTHERBOARD STATUS
MASK TO GET PI FLAG
NO INPUT TYPED YET
READ DATA FROM KEYBOARD
SAVE DATA FROM A-REGISTER
LOAD COMMAND BYTE TO A-REGISTER
RESET PI FLAG
RES'roRE DATA TO A-REGISTER
North Star HORIZON Computer
78