IBM PC CONVERTIBLE Technical Reference page 210

POST Interval Services (POST _INTV)
032A
I NT 15H
ROUTINE-NAME: POSLINTV (AH
=
83H)
FUNCTION: POST USER WHEN ELAPSED TIME INTERVAL HAS EXPIRED WITH NO
WAIT. (RETURNS IMMEDIATELY AND POSTS OCCURRENCE VIA RTC
INTERRUPTS)
INPUT: AL
=
0 SET UP FOR POST ON ELAPSED TIME INTERVAL
ES: BX POINTER TO BYTE IN CALLERS STORAGE FOR POST
CX,DX NUMBER OF MICROSECONDS TO ELAPSE BEFORE POSTING
(CX MOST SIGNIFICANT)
AL
=
1 CANCEL THE INTERVAL POST
OUTPUT: FOR POST SET - RTC PERIODIC INTERRUPT IS ACTIVATED TO KEEP
TRACK OF ELAPSED TIME. INTERRUPTS AT
APPROXIMATELY A 1 MILLISECOND RATE. WHEN TIME
HAS ELAPSED THE USER FLAG POINTED BY ES:BX WILL
HAVE BIT 7 SET TO A 1. THE PERIODIC INTERRUPT
WILL THEN BE TURNED OFF.
FOR CANCEL - RTC PERIODIC INTERRUPT IS TURNED OFF AND THE
POST ACTIVE FLAG IS RESET.
REGISTERS
MODIFIED: AX
POSLINTV PROC NEAR
032A B4 OB MOV AH, RTCMODE SET REGISTER NUMBER FOR RTC
CHECK FOR SET 032C 3C 00 CMP AL,O
032E 74 14 JE POSTLI MUST BE CLEAR
CANCEL ANY OUTSTANDING INTERVAL
0330 9C PUSHF DISABLE INTERRUPTS
0331 E8 0000 E CALL
o
I SA BL E_NM I AND 8259 INTERRUPTS
0334 E8 0000 E CALL GELRTCREG GET MODE
0337 24 BF AND AL, NOT PIE_ENABLE RESET PERIODIC IRPT ENABLE
0339 E8 0000 E CALL PULRTCREG ; SET MODE
033C
80 26 OOAO R FE AND RTCWAILFLAG,NOT INTERVAL_WAIT; RST INTVL ACTIVE
0341
EB 37 90 JMP POSTL3 ; ENABLE INTERRUPTS AND EXIT
; SET INTERVAL UNLESS ALREADY ACTIVE
0344
POSTLI :
0344 F6 06 OOAO R 01
TEST
JZ
RTCWAILFLAG, INTERVAL_WAIT CHECK WAIT IN PROG
0349 74 04
POSTL2
WAIT IS ACTIVE SO SIGNAL ERROR
034B
F9 STC
034C
EB 31 90 JMP POSTI_EXIT
ACTIVATE RTC PERIODIC INTERRUPT
034F
POSTL2:
034F
9C PUSHF
0350 E8 0000 E CALL
DISABLLNMI
0353 8C 06 009A R MOV
USER-FLAG....SEG, ES
0357 89 IE 0098 R MOV USER_FLAG, BX
035B 89 DE 009E R
MOV RTCHIGH,CX
035F 89 16 009C R
MOV RTCLOW,DX
SET ERROR
RETURN
DISABLE INTERRUPTS
SET UP TRANSFER TABLE
ROM BIOS 2-185