Technical information

TECHNICAL INFORMATION
Assembly-language programmers can use the following listing to
relocate the real-time clock code.
ISR
USR
EXI
CLK
SEC
MIN
HOURS
22
7FA8H
7FC1H
VIA BASIC USR(N)
ORG
EQU
; ENTRY
DI
CALL
XOR
OR
JR
1M
LD
LD
LD
LD
EI
JP
; REAL
EQU
EQU
EQU
EQU
PUSH
PUSH
LD
BIT
JR
BIT
JR
LD
INC
LD
CP
JR
XOR
LD
INC
INC
LD
CP
JR
XOR
LD
OA7FH
A
L
Z,EXI
1
A,OC3H
(4012H) ,A
HL,ISR
(4013H),HL
OA9AH
TIME CLOCK CODE
405EH
405FH
4060H
4061H
HL
AF
A, (37EOH)
6,A
NZ,FDC
7,A
Z,XIT
HL,CLK
(HL)
A, (HL)
40
C,XIT
A
(HL) ,A
HL
(HL)
A, (HL)
60
C,XIT
A
(HL) ,A
SET TO ISR START ADDR
DISABLE INTERRUPT
GET (HL)
IS USR ARG=O?
IF YES THEN EXIT
ELSE LINK
TO ISR
PUT IN JUMP TO ISR
START ADDR OF ISR
ENABLE INTERRUPT
TICKS
STORED HERE
SECONDS HERE
MINUTES HERE
SAVE REGISTERS
GET INTERRUPT STATUS
IF FDC MAKING RQST
EXIT IF INVALID INTRPT
HL => TICKS COUNTER
UPDATE "TICK"
40 TICKS PER SECOND
IF NO CARRY INTO SECS
RESET TIKCNT
POINT
TO SECONDS-COUNT
AND UPDATE
GET SECONDS COUNT
DONE IF NO CARRY TO HRS
ELSE RESET SECONDS