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COM Port now working - int14 fix #71

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c2fde07
int14 fix
Martin1701 Mar 19, 2026
b0fc467
int14 fix changes
Martin1701 Mar 25, 2026
ccb50a4
matching fd post behavior
Martin1701 Mar 25, 2026
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13 changes: 7 additions & 6 deletions src/GLABIOS.ASM
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Original file line number Diff line number Diff line change
Expand Up @@ -531,6 +531,8 @@ TURBO_TYPE = TURBO_NONE ; disable Turbo features
SW1_VID = 10b ; SW1 5/6 ON/OFF Video Type CGA 80
SW1_FLP = 1 ; SW1 7/8 Max # of floppy drives (0-3)
; 0-based: 0=1 drive, 1=2 drives, etc
POST_TEST_SEEK = 0 ; disabe floppy drive seek test
CGA_SNOW_REMOVE = 0 ; disable CGA snow removal
ENDIF

IF ARCH_TYPE EQ ARCH_EMU
Expand Down Expand Up @@ -6235,8 +6237,6 @@ INT_14_1 PROC
ADD DX, COM1_MCR-COM1_DATA ; DX = 3FC/2FC - Modem Control Register
MOV AL, MASK RTS OR MASK DTR ; activate DTR & RTS
OUT DX, AL ; set DTR or RTS
INC DX
INC DX ; DX = 3FE - Modem Status Register
MOV BX, DBW <MASK THRE OR MASK LBI, MASK MDSR> ; BH = line (THRE)
; BL = modem (DSR/CTS)
CALL INT_14_POLL ; poll both registers, AH = status
Expand Down Expand Up @@ -6269,11 +6269,10 @@ INT_14_2 PROC
ADD DX, COM1_MCR-COM1_DATA ; DX = 3FC/2FC - Modem Control Register
MOV AL, MASK DTR ; activate DTR
OUT DX, AL ; set DTR
INC DX
INC DX ; DX = 3FE/2FE - Modem Status Register
MOV BX, DBW <MASK MDSR, MASK LDR> ; BH = modem (DSR), BL = line (data ready)
CALL INT_14_POLL ; poll both registers, AH = status
POP DX ; restore base port
JNZ INT_14_RW_ERR ; Jump if port timeout
AND AH, MASK LBI OR MASK LFE OR MASK LPE OR MASK LOE ; include only
; error bits in port status
IN AL, DX ; read char from buffer
Expand All @@ -6285,7 +6284,7 @@ INT_14_2 ENDP
;----------------------------------------------------------------------------;
; Input:
; DI = port index (0 based byte)
; DX = 3FE Modem Status Register
; DX = 3FC Modem Status Register
; BL = line status expected masked
; BH = modem status expected masked
; Output:
Expand All @@ -6296,6 +6295,8 @@ INT_14_2 ENDP
; Clobbers: AX, CX
;----------------------------------------------------------------------------;
INT_14_POLL PROC
INC DX
INC DX ; DX = 3FE/2FE - Modem Status Register
CALL INT_14_POLL_PORT ; first poll modem status
JNZ INT_14_POLL_RET ; jump if ZF = 0, timeout or failure occurred
XCHG BH, BL ; BH = line status
Expand All @@ -6318,7 +6319,7 @@ INT_14_POLL_LOOP:
JZ INT_14_POLL_DONE
LOOP INT_14_POLL_LOOP ; poll port 65,535 * timeout times
DEC SI ;
JNZ INT_14_POLL_LOOP ; Jump if timeout not expired
JNS INT_14_POLL_LOOP ; Jump if timeout not expired
INT_14_POLL_DONE:
POP SI
INT_14_POLL_RET:
Expand Down