171 lines
4.4 KiB
NASM
171 lines
4.4 KiB
NASM
; ***************************************************************************
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; copyright : (C) 2023 by Martin Preuss
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; email : martin@libchipcard.de
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;
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; ***************************************************************************
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; * This file is part of the project "AqHome". *
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; * Please see toplevel file COPYING of that project for license details. *
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; ***************************************************************************
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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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; - X: pointer to allocated buffer in SRAM
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; MODIFIED REGISTERS: r16, r17, r21
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COM2_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, com2RecvBuffersUsed
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cpi r17, COM2_BUFFER_NUM
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brcc COM2_AllocBuffer_error ; no buffer available
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inc r17 ; increment number of buffers used
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sts com2RecvBuffersUsed, r17 ; store new value
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lds r16, com2MaxBuffersUsed ; calc max buffers used
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cp r16, r17
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brcc COM2_AllocBuffer_l0
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sts com2MaxBuffersUsed, r17
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COM2_AllocBuffer_l0:
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lds r16, com2RecvBuffersWritePos ; 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, COM2_BUFFER_NUM ; CF set if COM_BUFFER_NUM > R17
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brcs COM2_AllocBuffer_l1
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clr r17 ; wraparound
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COM2_AllocBuffer_l1:
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sts com2RecvBuffersWritePos, r17 ; store new writepos for next caller
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rcall COM2_BufferPosToX ; (R16, R17)
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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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COM2_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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; COM2_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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COM2_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, com2RecvBuffersUsed
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tst r17
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breq COM2_BufferDeallocBack_error ; no buffer allocated, nothing to release
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dec r17
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sts com2RecvBuffersUsed, r17 ; store new value
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lds r17, com2RecvBuffersWritePos
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tst r17 ; 0?
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brne COM2_BufferDeallocBack_l1 ; nope go directly decrement r17
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ldi r17, COM2_BUFFER_NUM ; wrap-around
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COM2_BufferDeallocBack_l1:
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dec r17
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sts com2RecvBuffersWritePos, r17
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out SREG, r21
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sec
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ret
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COM2_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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; COM2_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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COM2_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, com2RecvBuffersUsed
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tst r17
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breq COM2_BufferDeallocFront_error ; no buffer allocated, nothing to release
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dec r17
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sts com2RecvBuffersUsed, r17 ; store new value
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lds r17, com2RecvBuffersReadPos
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inc r17
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cpi r17, COM2_BUFFER_NUM
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brcs COM2_BufferDeallocFront_l1
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clr r17 ; wrap-around
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COM2_BufferDeallocFront_l1:
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sts com2RecvBuffersReadPos, r17
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out SREG, r21
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sec
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ret
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COM2_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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; COM2_BufferPosToX
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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 COM2_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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; - X: pointer to buffer in SRAM
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; MODIFIED REGISTERS: R16, R17
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COM2_BufferPosToX:
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; calculate offset
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clr r17
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mov xl, r16
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clr xh
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lsl xl
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rol xh ; *2
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add xl, r16
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adc xh, r17 ; *3
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lsl xl
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rol xh ; *6
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lsl xl
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rol xh ; *12
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lsl xl
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rol xh ; *24
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; add base position of buffers
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ldi r16, LOW(com2RecvBuffers)
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ldi r17, HIGH(com2RecvBuffers)
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add xl, r16
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adc xh, r17
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ret
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