4e1f08b567
- prepared for use of CRC8 - organized code in more files - recv stats message now contains crc errors and io errors
164 lines
3.9 KiB
NASM
164 lines
3.9 KiB
NASM
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; ***************************************************************************
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; code
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.cseg
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; ---------------------------------------------------------------------------
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; COM_BufferAlloc
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;
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; Allocate a transfer buffer.
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear otherwise
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; - Y: pointer to allocated buffer in SRAM
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; MODIFIED REGISTERS: r16, r17, r21
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COM_BufferAlloc:
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in r21, SREG ; save global interrupt enable bit from SREG
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cli
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lds r17, comRecvBuffersUsed
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cpi r17, COM_BUFFER_NUM
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brcc COM_AllocBuffer_error ; no buffer available
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inc r17 ; increment number of buffers used
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sts comRecvBuffersUsed, r17 ; store new value
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lds r16, comRecvBuffersWritePos ; get current write pos
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mov r17, r16 ; increment for next call
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inc r17
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cpi r17, COM_BUFFER_NUM ; CF set if COM_BUFFER_NUM > R17
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brcs COM_AllocBuffer_l1
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clr r17 ; wraparound
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COM_AllocBuffer_l1:
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sts comRecvBuffersWritePos, r17 ; store new writepos for next caller
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rcall COM_BufferPosToY ; (R16, R17)
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clr r17
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std y+COM_BUFFER_OFFS_FLAGS, r17 ; preset flags
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out SREG, r21 ; restore global interrupt enable bit in SREG
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sec
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ret
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COM_AllocBuffer_error:
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out SREG, r21
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clc
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ret
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; ---------------------------------------------------------------------------
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; COM_BufferDeallocBack
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;
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; Release a transfer buffer at the end of the list by decreasing the write pos.
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; This releases the last allocated buffer!
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;
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear otherwise
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; MODIFIED REGISTERS: r16, r17, r21
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COM_BufferDeallocBack:
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in r21, SREG ; save global interrupt enable bit from SREG
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cli
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lds r17, comRecvBuffersUsed
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tst r17
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breq COM_BufferDeallocBack_error ; no buffer allocated, nothing to release
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dec r17
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sts comRecvBuffersUsed, r17 ; store new value
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lds r17, comRecvBuffersWritePos
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tst r17 ; 0?
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brne COM_BufferDeallocBack_l1 ; nope go directly decrement r17
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ldi r17, COM_BUFFER_NUM ; wrap-around
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COM_BufferDeallocBack_l1:
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dec r17
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sts comRecvBuffersWritePos, r17
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out SREG, r21
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sec
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ret
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COM_BufferDeallocBack_error:
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out SREG, r21
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clc
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ret
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; ---------------------------------------------------------------------------
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; COM_BufferDeallocFront
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;
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; Release a transfer buffer by increasing the read pos.
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;
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear otherwise
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; MODIFIED REGISTERS: r16, r17, r21
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COM_BufferDeallocFront:
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in r21, SREG ; save global interrupt enable bit from SREG
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cli
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lds r17, comRecvBuffersUsed
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tst r17
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breq COM_BufferDeallocFront_error ; no buffer allocated, nothing to release
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dec r17
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sts comRecvBuffersUsed, r17 ; store new value
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lds r17, comRecvBuffersReadPos
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inc r17
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cpi r17, COM_BUFFER_NUM
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brcs COM_BufferDeallocFront_l1
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clr r17 ; wrap-around
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COM_BufferDeallocFront_l1:
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sts comRecvBuffersReadPos, r17
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out SREG, r21
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sec
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ret
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COM_BufferDeallocFront_error:
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out SREG, r21
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clc
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ret
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; ---------------------------------------------------------------------------
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; COM_BufferPosToY
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;
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; Get a pointer to the SRAM position of the given buffer.
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; CAVE: Code must correspond to COM_BUFFER_SIZE!!
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; IN:
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; - R16: buffer number (starting with 0)
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; OUT:
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; - Y: pointer to buffer in SRAM
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; MODIFIED REGISTERS: R16, R17
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COM_BufferPosToY:
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; calculate offset
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clr r17
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mov yl, r16
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clr yh
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lsl yl
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rol yh ; *2
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add yl, r16
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adc yh, r17 ; *3
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lsl yl
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rol yh ; *6
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lsl yl
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rol yh ; *12
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lsl yl
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rol yh ; *24
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; add base position of buffers
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ldi r16, LOW(comRecvBuffers)
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ldi r17, HIGH(comRecvBuffers)
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add yl, r16
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adc yh, r17
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ret
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