;******************************************************************
　　;  RS232的傳送與接收子程序 修改自serialb.asm
　　;******************************************************************
　　
　　;label:          XPAGEON
　　
　　;
　　; Variable memory allocations
　　innerDelayOneCount:       equ 3Ch ; Delay One: Inner delay count 
　　outerDelayOneCount:       equ 3Dh ; Delay One: Outer delay count 
　　innerDelayCount:          equ 3Eh ; Delay: Inner delay count 
　　outerDelayCount:          equ 3Fh ; Delay: Outer delay count 
　　rxEnable:                 equ 40h ; Receiver Enabled Flag
　　rxBitCount:               equ 42h ; Recieve Bits Count
　　rxFrameCount:             equ 4dh ; Recieve Frame Count
　　rxData:		          equ 46h ; Receive Data Holding Register
　　rxBufPtr:                 equ 48h ; Receive Buffer Pointer
　　rxFrameFlag:              equ 4Ah ; Framing Error Flag (0=No,1=Yes)
　　rxPassCount:              equ 4Bh ; Transmit Buffer Pointer
　　rxBuf:		          equ 50h ; Recieve Buffer Start
　　rxBufEnd:                 equ 5Fh ; Recieve Buffer End
　　txEnable:                 equ 4eh ; Transmiter Enabled Flag
　　txBitCount:               equ 43h ; Transmit Bits Count
　　txFrameCount:             equ 45h ; Transmit Frame Count
　　txData:		          equ 47h ; Transmit Data Holding Register
　　txBufPtr:                 equ 49h ; Transmit Buffer Pointer
　　txBuf:		          equ 4Ch ; Transmit Buffer Start (4 Bytes)
　　;
　　; Constant declarations
　　; Transmit counter values
　　txStart:	  equ 00h ; Start bit begin
　　txBit0:	    equ 03h ; Start bit end
　　txBit1:	    equ 07h ; Data bit 0 end
　　txBit2:	    equ 0Ah ; Data bit 1 end
　　txBit3:	    equ 0Dh ; Data bit 2 end
　　txBit4:	    equ 10h ; Data bit 3 end
　　txBit5:	    equ 14h ; Data bit 4 end
　　txBit6:	    equ 17h ; Data bit 5 end
　　txBit7:	    equ 1Ah ; Data bit 6 end
　　txStop:	    equ 1Dh ; Data bit 7 end
　　txComp:	    equ 20h ; Stop bit end
　　;
　　txDataMask: equ FEh ; Mask to preserve inputs.
　　;
　　; Receive counter values
　　rxStart:    equ 01h ; Start bit center
　　rxBit0:	    equ 05h ; Data bit 0 center
　　rxBit1:	    equ 09h ; Data bit 1 center
　　rxBit2:	    equ 0Ch ; Data bit 2 center
　　rxBit3:	    equ 0Fh ; Data bit 3 center
　　rxBit4:	    equ 12h ; Data bit 4 center
　　rxBit5:	    equ 16h ; Data bit 5 center
　　rxBit6:	    equ 19h ; Data bit 6 center
　　rxBit7:	    equ 1Ch ; Data bit 7 center
　　rxStop:	    equ 1Fh ; Data bit 7 center
　　rxComp:	    equ 22h ; Stop bit center
　　lastrxBit:  equ 07h ; Last receive data bit count
　　;4
　　; Interrupt masks
　　GPIO_intMask:	  equ 40h ; Mask for Port 0 GPIO interrupts.
　　128us_intMask:    equ 02h ; Mask to enable 128us only.
　　;
　　; ASCII Characters for commands
　　Car_Ret:          equ 0Dh ; Carriage Return Terminator
　　Ln_Fd:            equ 0Ah ; Line Feed Terminator
　　Asc_Space:        equ 20h ; ASCII Space Character
　　;
　　;************************************************************************
　　; If we are recieving a byte of data from the serial channel we need to
　　; go to the receive subroutine.
　　
　　Serial_ISR:
　　	push	A                     ;
　　	push X                      ;
　　;	mov	A, [rxEnable]           ; Load the receive enable flag.
　　;	cmp	A, 0 			              ; Check for receive in progress.
　　;	jnz	Increment_rxFrameCount  ; Yes, go receive.
　　;************************************************************************
　　; If we are sending a byte of data to the serial channel we need to
　　; go to the transmit subroutine.
　　;
　　	mov	A, [txEnable]           ; Check for transmit in progress.
　　	cmp	A, 0                    ;
　　	jnz	Increment_txFrameCount  ; Yes, go transmit.
　　	jmp	done_Serial             ; Default
　　;
　　; We are transmitting.
　　Increment_txFrameCount:
　　	inc	[txFrameCount]          ; Adjust frame count.
　　	mov	A, [txFrameCount]       ; Put it in the accumulator
　　	mov	[txBitCount], A         ; Save it as the new bit count
　　	jmp	done_Serial             ; Finished
　　;
　　; We are receiving.
　　;Increment_rxFrameCount:
　　	inc	[rxFrameCount]          ; Adjust frame count.
　　	call	rxRoutine             ; Go get a character
　　	pop X                       ;
　　	mov	A, 00h                  ; Disable interrupts and return.
　　	ipret	Global_Interrupt      ;
　　;
　　; Finish the interrupt handling
　　done_Serial:
　　	pop X
　　	mov	A, 128us_intMask        ; Load 128us ISR Enable value
　　	ipret	Global_Interrupt      ; Return and enable 128us ISR
　　;
　　;************************************************************************
　　; The GPIO interrupt will occur at the start of a receive data byte.
　　; The low going start bit will trigger the GPIO_ISR.
　　;
　　GPIO_ISR:
　　	push	A	; save the accumulator to stack
　　	push	X	; save X on stack
　　
　　; Three steps for detecting the start bit:
　　; 1.) Check that the receiver generated the interrupt.
　　;       iord    [Port0_Data]    
　　;       and     A, 80h          
　　;       jz      GPIO_ISR_Done   
　　;       jnz     GPIO_ISR_Done   
　　
　　; 2.) Set the receive enable bit.
　　	mov	A, 01h		          ; Load the accumulator.
　　        mov     [rxEnable], A             ; write to the receive enable flag.
　　;
　　; 3.) Clear the receive data register.
　　	mov	A, 00h		          ; Clear the accumulator.
　　        mov     [rxData], A               ; Clear the receive data register.
　　GPIO_ISR_Done:
　　        pop     x                         ; Restore the index register.
　　	mov	A, 128us_intMask	  ; Load the 128us interrupt mask.
　　        ipret   Global_Interrupt          ; Return to caller.
　　                                          ; 128us interrupt enabled.
　　;
　　;************************************************************************
　　; During serial transfers data bit 0 is transmitted first.
　　; We will use Port 0 Bit 7 for receive and Bit 0 for transmit.
　　; Data will always be right shifted for either transmit or receive.
　　; Port 0 Bit 7 will be a falling edge sensitive GPIO_ISR input.
　　; Port 0 bits 6-0 and Port 1 bits 3-0 will be outputs.
　　;
　　SerialInitialize:
　　	push	A			        ; Save the accumulator.
　　	push	X			        ; Save the index.
　　	mov	A, FFh		      ; load accumulator with ones
　　	iowr	Port0_Data		; output ones to port 0
　　	iowr	Port1_Data		; output ones to port 1
　　
　　	mov	A, 00h		; load accumulator with zeros
　　	iowr	Port0_Pullup	; enable port 0 pullups
　　	iowr	Port1_Pullup	; enable port 1 pullups
　　;
　　	iowr	Port0_Interrupt	; disable port 0 interrupts
　　	iowr	Port1_Interrupt	; disable port 1 interrupts
　　;
　　	mov	A, 08h		      ; load accumulator with med sink
　　	iowr	Port0_Isink0	; minimum sink current Port0 bit 0
　　;
　　;	iowr	Watchdog		  ; clear watchdog timer
　　;
　　; Clear the serial channel counters.
　　	mov	A, 00h
　　	mov	[rxEnable], A	    ; Clear rxEnable Flag
　　	mov	[rxBitCount], A	  ; Clear rx bit count.
　　	mov	[rxFrameCount], A	; Clear rx frame counter.
　　	mov	[rxBufPtr], A	    ; Clear rx buffer Pointer.
　　	mov	[txEnable], A	    ; Clear txEnable Flag.
　　	mov	[txBitCount], A	  ; Clear tx bit count.
　　	mov	[txFrameCount], A	; Clear tx frame counter.
　　	mov	[txBufPtr], A	    ; Clear tx buffer Pointer.
　　
　　	mov	A, 81h		        ; Enable port0 bit7 as input.
　　	iowr	Port0_Data		  ; All other bits are outputs.
　　	mov	A, 7Eh		        ; Select falling edge interrupt
　　	iowr	Port0_Pullup	  ; on port0 bit7.
　　	mov	A, 00h		        ;
　　	iowr	Port0_Interrupt	; Disable port 0 bit 7 interrupt.
　　
　　	mov	[txBufPtr], A	      ; Reset tx buffer pointer.
　　; 	mov	[interrupt_mask], A ; Default all interrupts to disabled.
　　	pop	X			              ; Restore the index.
　　	pop	A			              ; Restore the accumulator.
　　	ret				              ; Return to caller.
　　
　　;************************************************************************
　　; TX_Data processing:
　　; This routine will write a byte of data.
　　; 1.) Send the active low Start bit.
　　; 2.) Send eight variable data bits.
　　; 3.) Send the active high Start bit.
　　; 4.) Stay in transmit until complete.
　　;************************************************************************
　　;
　　txRoutine:
　　;  Prepare for the transmit.
　　        push    A                         ; save accumulator.
　　        mov     A, 01h                    ; Load txEnable Flag.
　　        mov     [txEnable], A             ; Store txEnable Flag.
　　        mov     A, [txFrameCount]         ; Get frame count.
　　        mov     [txBitCount], A           ; Save bit count.
　　;
　　sendStart:
　　;  Write out the start bit. (active low)
　　	mov	A, FEh		          ; Load tx Start bit.
　　        iowr    Port0_Data                ; Send tx Start bit.
　　        mov     A, 02h                    ; Load 128us ISR Enable value.
　　        iowr    Global_Interrupt          ; Enable 128us ISR.
　　;
　　;  Check the bit count and send a bit if required.
　　check_tx_bit:
　　	mov	A, [txBitCount]	; Get frame count
　　	cmp	A, txBit0		; tx bit 0 at frame count=03h
　　	jz	sendtxBit		; Go send data bit
　　	cmp	A, txBit1		; tx bit 1 at frame count=07h
　　	jz	sendtxBit		; Go send data bit
　　	cmp	A, txBit2		; tx bit 2 at frame count=0Ah
　　	jz	sendtxBit		; Go send data bit
　　	cmp	A, txBit3		; tx bit 3 at frame count=0Dh
　　	jz	sendtxBit		; Go send data bit
　　	cmp	A, txBit4		; tx bit 4 at frame count=10h
　　	jz	sendtxBit		; Go send data bit
　　	cmp	A, txBit5		; tx bit 5 at frame count=14h
　　	jz	sendtxBit		; Go send data bit.
　　	cmp	A, txBit6		; tx bit 6 at frame count=17h.
　　	jz	sendtxBit		; Go send data bit.
　　	cmp	A, txBit7		; tx bit 7 at frame count=1Ah.
　　	jz	sendtxBit		; Go send data bit.
　　	cmp	A, txStop		; tx Stop at frame count=1Dh.
　　	jz	sendStop		; Go send stop bit.
　　	cmp	A, txComp		; tx Stop at frame count=20h.
　　	jz	txEnd			  ; Go send end transmit.
　　	jmp	check_tx_bit	; Wait for the next interrupt.
　　;
　　sendtxBit:
　　;  Transmit the current data bit and adjust for next pass.
　　	mov	A, [txData]		  ; Get the current data.
　　	or	A, txDataMask	  ; Mask out inputs.
　　	iowr	Port0_Data	  ; Output the current data bit.
　　	mov	A, [txData]		  ; Get the current data.
　　	asr	A			          ; Align next data bit.
　　	mov	[txData], A		  ; Save adjusted data.
　　	mov	A, FFh		      ; Fill the accumulator.
　　	mov	[txBitCount], A ; Write to bit counter.
　　	jmp	check_tx_bit	  ; Wait for next bit time.
　　;
　　sendStop:
　　;  The data has been sent, now send the stop bit.
　　	mov	A, FFh		      ; Load stop bit.
　　	iowr	Port0_Data		; Send stop bit.
　　	jmp	check_tx_bit	  ; Go to end of transmit.
　　;
　　txEnd:
　　;  The last data bit has been sent.
　　;  Clean up and return. 
　　;	mov	A, 00h		          ; Clear the accumulator.
　　;       mov     [interrupt_mask],A        ; Load into the mask.
　　	mov	a,[interrupt_mask]
　　        iowr    Global_Interrupt          ; Disable all interrupts.
　　	mov	A, 00h		          ; Load tx Start bit.
　　        mov     [txBitCount], A           ; Clear tx bit count.
　　	mov	[txFrameCount], A	  ; Clear tx frame counter.
　　        mov     [txEnable], A             ; Clear the tx enadle flag.
　　	mov	[rxFrameCount], A	  ; Clear rx frame counter.