IBM PC CONVERTIBLE Technical Reference page 232

0764 E6 43 OUT
TI M ER_CTL ,AL
WRITE TO TIMER CONTROL PORT
0766
BB 0533 MOV AX,533H DIVISOR FOR 1000 HZ
0769 E6 42 OUT TIMER2,AL
TIMER 2 COUNT LSB
076B 8A C4
MOV AL,AH
076D E6 42 OUT TIMER2,AL
TIMER 2 COUNT MSB
076F E4 61 IN AL, NMLCNTL GET SPEAKER ENABLE BIT
Onl
8A EO MOV AH,AL ; SAVE SPEAKER ENABLE SETTING
on3
DC 03 OR AL,SPKR_DATA+TMRLGATE ; ENABLE SPEAKER
On5
F6 C3 80 TEST BL, FRCBEP ; CHECK FOR FORCED BEEP BIT
On8
74 02 JZ BP10 ; JUMP I F NOT FORCED BEEP
anA DC 04 BP5 : OR AL, EN_SPKR ; SET SPEAKER ENABLE BIT
onc
E6 61 BPI0: OUT NMLCNTL,AL ; TURN ON SPEAKER ENABLE
onE BO E3 7F AND BL, a FFH- FRCBEP
MASK OUT FORCED BEEP BIT
0781 B9 0000 MOV CX,O SET CNT TO WAIT 500 MSECS
0784 E2 FE BP15: LOOP BP15 WAIT 500 MSECS
0786 FE CB DEC BL DECREMENT COUNTER
0788 75 FA JNZ BP15
LOOP I F COUNT NOT ZERO
078A 8A C4 BP20 : MOV AL,AH
SET PREVIOUS PORT SETTING
078C E6 61 OUT NMLCNTL ,AL
SEND TO PPI
078E B8 FOOD MOV AX ,OFOOOH CH ECK FOR ROM STACK
0791 8C D3 MOV BX,SS
0793 3B C3 CMP AX,BX
0795 74 03 JE BEEP _EXT IF ROM STACK THEN RETURN
0797 59 POP CX RESTORE REGISTERS
0798 5B POP BX
0799 58 POP AX
079A
BEEP _EXT:
079A C3 RET
RETURN
079B BEEP ENDP
Disable All Interrupts (DISABLE_NMI)
079B
079B FA
079C 50
079D 80 07
079F E6 72
07 Al 58
07 A2 C3
07A3
DISABLE ALL INTERRUPTS
**************************
DISABLE_NMI
CLI
PUSH
AX
PROC
NEAR
; DISABLE MASKABLE INTERRUPTS
MOV AL,DISABLE_SLEEP+CLOCLRUN ; DISABLE NMIS
OUT CLOCLCTL,AL ; WRITE TO PORT
POP AX
RET
DISABLE_NMI ENDP
Enable Global NMIs (ENABLE_NMI)
*************************************************************
ENABLE GLOBAL NMI' S
*************************************************************
07A3
ENABLE_NMI
PROC NEAR
07A3 50 PUSH AX
ROM BIOS 2-207