GMS81004 Datasheet, PDF (99/101 Pages) Hynix Semiconductor – 8-BIT SINGLE CHIP MICROCOMPUTERS

Appendix B. PROGRAMMER`S GUIDE
Key Scan
- To secure the key board scanning , read the input port after minimum 60uS delay time from
output port set to `Low `. This time delay is for the port rising time depend on the
input pull-up resistor .
; program example ,See the circuit B-1
.
ldm R1,#1111_1110b
call delay_60uS
lda R0
.
.
;R10 port set to LOW
;60uS time delay routine
;R0 port Read
R0 port Read timing
R10
60uS
R11
60uS
Fig B-2 , Input with pull-up port read time method
B -3