ser1.asm

汇编编程艺术

;
; Routines to handle COM1 data transmission.
;
; COM1 refers to HARDWARE COM1 port which is located beginning at port
; address 3f8h and causes INT 0Ch.
;
;
; Released to the public domain.
; Created by Randall Hyde.
; Date: 8/11/90
;
;
; Useful equates:
;
BIOSvars	=	40h
Com1Adrs	=	0
Com2Adrs	=	2
;
BufSize		=	256			;# of bytes in buffer.
;
;
; Serial port equates:
;
Com1Port	=	3F8h
Com1IER		=	3F9h
Com1IIR		=	3FAh
Com1LCR		=	3FBh
Com1MCR		=	3FCh
Com1LSR		=	3FDh
Com1MSR		=	3FEh
;
;
; Register assignments:
;
; Interupt enable register (IER):
;
;		If one:
; bit 0-	Enables received data available interrupt.
; bit 1-	Enables transmitter holding register empty interrupt.
; bit 2-	Enables receiver line status interrupt.
; bit 3-	Enables the modem status interrupt.
; bits 4-7-	Always set to zero.
;
; Interrupt ID Register (IIR):
;
; bit 0-	No interrupt is pending (interrupt pending if zero).
; bits 1,2-	Binary value denoting source of interrupt:
;			00-Modem status
;			01-Transmitter Hold Register Empty
;			10-Received Data Available
;			11-Receiver line status
; bits 3-7	Always zero.
;
;
; Line Control Register (LCR):
;
; bits 0,1-	Word length (00=5, 01=6, 10=7, 11=8 bits).
; bit 2-	Stop bits (0=1, 1=2 stop bits [1-1/2 if 5 data bits]).
; bit 3-	Parity enabled if one.
; bit 4-	0 for odd parity, 1 for even parity (assuming bit 3 = 1).
; bit 5-	1 for stuck parity.
; bit 6-	1=force break.
; bit 7-	1=Divisor latch access bit.  0=rcv/xmit access bit.
;
; Modem Control Register (MCR):
;
; bit 0-	Data Terminal Ready (DTR)
; bit 1-	Request to send (RTS)
; bit 2-	OUT 1
; bit 3-	OUT 2
; bit 4-	Loop back control.
; bits 5-7-	Always zero.
;
; Line Status Register (LSR):
;
; bit 0-	Data Ready
; bit 1-	Overrun error
; bit 2-	Parity error
; bit 3-	Framing error
; bit 4-	Break Interrupt
; bit 5-	Transmitter holding register is empty.
; bit 6-	Transmit shift register is empty.
; bit 7-	Always zero.
;
; Modem Status Register (MSR):
;
; bit 0-	Delta CTS
; bit 1-	Delta DSR
; bit 2-	Trailing edge ring indicator
; bit 3-	Delta carrier detect
; bit 4-	Clear to send
; bit 5-	Data Set Ready
; bit 6-	Ring indicator
; bit 7-	Data carrier detect
;
;
;
;
;
;
;
StdGrp		group	StdLib, StdData
;
;
;
;
StdData		segment	para public 'sldata'
;
int0Cofs	equ	es:[30h]
int0Cseg	equ	es:[32h]
int0cVec	dd	?		;Holds old int 0ch vector.
InHead		dw	InpBuf
InTail		dw	InpBuf
InpBuf		db	Bufsize dup (?)
InpBufEnd	equ	this byte
;
OutHead		dw	OutBuf
OutTail		dw	OutBuf
OutBuf		db	BufSize dup (?)
OutBufEnd	equ	this byte
;
i8259a		db	0		;8259a interrupt enable register.
TestBuffer	db	0		;1 means we are transmitting out of
;					; the transmit buffer.  0 means the
;					; transmitter register is empty and
;					; we can store data directly to it.
StdData		ends
;
;
;
stdlib		segment	para public 'slcode'
		assume	cs:StdGrp
;
;
;
; sl_Com1Baud: Set the COM1 port baud rate
; AX = baud rate (110, 150, 300, 600, 1200, 2400, 4800, 9600, 19200)
;
		public	sl_Com1Baud
sl_Com1Baud	proc	far
		push	ax
		push	dx
		cmp	ax, 9600
		ja	Set19200
		je	Set9600
		cmp	ax, 2400
		ja	Set4800
		je	Set2400
		cmp	ax, 600
		ja	Set1200
		je	Set600
		cmp	ax, 150
		ja	Set300
		je	Set150
		mov	ax, 1047		;Default to 110 baud
		jmp	short SetPort
;
Set150:		mov	ax, 768
		jmp	short SetPort
;
Set300:		mov	ax, 384
		jmp	short SetPort
;
Set600:		mov	ax, 192
		jmp	short SetPort
;
Set1200:	mov	ax, 96
		jmp	short SetPort
;
Set2400:	mov	ax, 48
		jmp	short SetPort
;
Set4800:	mov	ax, 24
		jmp	short SetPort
;
Set9600:	mov	ax, 12
		jmp	short SetPort
;
Set19200:	mov	ax, 6
SetPort:	mov	dx, ax			;Save baud value.
		call	far ptr sl_GetLCRCom1
		push	ax			;Save old divisor bit value.
		or	al, 80h			;Set divisor select bit.
		call	far ptr sl_SetLCRCom1
		mov	ax, dx			;Get baud rate divisor value.
		mov	dx, Com1Port
		out	dx, al
		inc 	dx
		mov	al, ah
		out	dx, al
		mov	dx, Com1LCR
		pop	ax
		call	far ptr sl_SetLCRCom1	;Restore divisor bit value.
		pop	dx
		pop	ax
		ret
sl_Com1Baud	endp
;
;
; sl_Com1Stop:
; Set the number of stop bits.
;
; AL=1 for one stop bit, 2 for two stop bits.
;
		public	sl_com1Stop
sl_com1Stop	proc	far
		push	ax
		push	dx
		dec	ax
		shl	ax, 1			;position into bit #2
		shl	ax, 1
		mov	ah, al
		mov	dx, Com1LCR
		in	al, dx
		and 	al, 11111011b		;Mask out Stop Bits bit
		or	al, ah			;Mask in new # of stop bits.
		out	dx, al
		pop	dx
		pop	ax
		ret
sl_com1Stop	endp
;
;
; sl_com1size: Sets word size on the com1 port.
; AX = 5, 6, 7, or 8 which is the number of bits to set.
;
		public	sl_com1size
sl_com1size	proc	far
		push	ax
		push	dx
		sub	al, 5
		cmp	al, 3
		jbe	Okay
		mov	al, 3			;Default to eight bits.
Okay:		mov	ah, al
		mov	dx, com1LCR
		in	al, dx
		and	al, 11111100b		;Mask out old word size
		or	al, ah			;Mask in new word size
		out	dx, al
		pop	dx
		pop	ax
		ret
sl_com1size	endp
;
;
; sl_com1parity: Turns parity on/off, selects even/odd parity, or stuck parity.
; ax contains the following:
;
; bit 0-	1 to enable parity, 0 to disable.
; bit 1-	0 for odd parity, 1 for even (only valid if bit 0 is 1).
; bit 2-	Stuck parity bit.  If 1 and bit 0 is 1, then the parity bit
;		is always set to the inverse of bit 1.
;
		public	sl_com1parity
sl_com1parity	proc	far
		push	ax
		push	dx
;
		shl	ax, 1
		shl	ax, 1
		shl	ax, 1
		and	ax, 00111000b		;Mask out other data.
		mov	ah, al
		mov	dx, com1LCR
		in	al, dx
		and	al, 11000111b
		or	al, ah
		out	dx, al
		pop	dx
		pop	ax
		ret
sl_com1parity	endp
;
;
;****************************************************************************
;
; Polled I/O:
;
;
; sl_ReadCom1-	Reads a character from COM1 and returns that character in
;		the AL register.  Synchronous call, meaning it will not
;		return until a character is available.
;
		public	sl_ReadCom1
sl_ReadCom1	proc	far
		push	dx
		call	far ptr sl_GetLCRCom1
		push	ax			;Save divisor latch access bit.
		and	al, 7fh			;Select normal port.
		call	far ptr sl_SetLCRCom1
		mov	dx, com1LSR
WaitForChar:	call	far ptr sl_GetLSRCom1
		test	al, 1			;Data Available?
		jz	WaitForChar
		mov	dx, com1Port
		in	al, dx
		mov	dl, al			;Save character
		pop	ax			;Restore divisor access bit.
		call	far ptr sl_SetLCRCom1
		mov	al, dl			;Restore output character.
		pop	dx
		ret
sl_ReadCom1	endp
;
;
;
; sl_WriteCom1-	Writes the character in AL to the com1 port.
;
		public	sl_WriteCom1
sl_WriteCom1	proc	far
		push	dx
		push	ax
		mov	dl, al			;Save character to output
		call	far ptr sl_GetLCRCom1
		push	ax			;Save divisor latch access bit.
		and	al, 7fh			;Select normal port.
		call	far ptr sl_SetLCRCom1
WaitForXmtr:	call	far ptr sl_GetLSRCom1
		test	al, 00100000b		;Xmtr buffer empty?
		jz	WaitForXmtr
		mov	al, dl			;Get output character.
		mov	dx, Com1Port
		out	dx, al
		pop	ax			;Restore divisor access bit.
		call	far ptr sl_SetLCRCom1
		pop	ax
		pop	dx
		ret
sl_WriteCom1	endp
;
;
;
; sl_TstInpCom1-Returns AL=0 if a character is not available at the com1 port.
;		Returns AL=1 if a character is available.
;
		public	sl_TstInpCom1
sl_TstInpCom1	proc	far
		push	dx
		mov	dx, com1LSR
		in	al, dx
		and 	al, 1
		pop	dx
		ret
sl_TstInpCom1	endp
;
;
; sl_TstOutCom1-Returns AL=1 when it's okay to send another character to
;		the transmitter.  Returns zero if the transmitter is full.
;
		public	sl_TstOutCom1
sl_TstOutCom1	proc	far
		push	dx
		mov	dx, com1LSR
		in	al, dx
		test	al, 00100000b
		mov	al, 0
		jz	toc1
		inc	ax
toc1:		pop	dx
		ret
sl_TstOutCom1	endp
;
;
; sl_GetLSRCom1-Returns the LSR in al:
;
; AL:
;	bit 0-	Data Ready
;	bit 1-	Overrun error
;	bit 2-	Parity error
;	bit 3-	Framing error
;	bit 4-	Break interrupt
;	bit 5-	Xmtr holding register is empty.
;	bit 6-	Xmtr shift register is empty.
;	bit 7-	Always zero.
;
		public	sl_GetLSRCom1
sl_GetLSRCom1	proc	far
		push	dx
		mov	dx, com1LSR
		in	al, dx
		pop	dx
		ret
sl_GetLSRCom1	endp
;
;
; sl_GetMSRCom1-Returns the modem status register in AL
;
; AL:
;	bit 0-	Delta clear to send
;	bit 1-	Delta data set ready
;	bit 2-	Trailing edge ring indicator
;	bit 3-	Delta data carrier detect
;	bit 4-	Clear to send (CTS)
;	bit 5-	Data set ready (DSR)
;	bit 6-	Ring indicator (RI)
;	bit 7-	Data carrier detect (DCD)
;
		public	sl_GetMSRCom1
sl_GetMSRCom1	proc	far
		push	dx
		mov	dx, com1MSR