243 lines
6.5 KiB
Plaintext
243 lines
6.5 KiB
Plaintext
.include "spi.h65"
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.include "system.h65"
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Export spi_p, irq_handler, end, status
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Export spi_p, begin_read, irq_read_byte, recv_bytes
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Export spi_p, begin_write, irq_write_byte, sent_bytes
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.zeropage
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buffer_start: .res 2
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.bss
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recv_bytes:
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sent_bytes: .res 2
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status: .res 1
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buffer_size: .res 2
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irq_handler: .res 2
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SPI_IO := spi_p::SPI_IO
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; spi-transferred code will be placed here
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; SPI_P = as peripheral
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.code
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;;********************************************************************************
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;; @function Begin listening for SPI transfers
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;;********************************************************************************
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.proc init
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lda #spi_p::STATUS::DONE
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sta status
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.endproc
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;;********************************************************************************
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;; @function Begin listening for SPI transfers
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;; @details
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;; The transfer must be: <SIZE, >SIZE, data (SIZE bytes)
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;;
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;; - initialize variables
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;; - configure shift register to shift in under external clock
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;; - enable shift register interrupts
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;; @param ARG0-1: Start address of the buffer
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;; @param ARG2-3: Size of the buffer
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;; @todo: Use irq register handler
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;; @note: The buffer must be large enough for the received data.
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;;********************************************************************************
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.proc begin_read
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stz recv_bytes
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stz recv_bytes+1
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lda #spi_p::STATUS::XFER_SIZEL
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sta status
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; store address in zp
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lda #<ARG0
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sta buffer_start
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lda #>ARG1
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sta buffer_start+1
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; load irq handler
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lda #<irq_read_byte
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sta irq_handler
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lda #>irq_read_byte
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sta irq_handler+1
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; temporarily store the low byte in buffer, will be checked later
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lda #<ARG2
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sta (buffer_start)
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lda #>ARG3
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sta buffer_size+1
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; set Shift register to shift in under external clock on CB1
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MaskedWrite SPI_IO+IO::ACR, #IO::ACR::SR_SIN_PHIE, #IO::ACR_MASK::SR
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; enable SR interrupts
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lda #(IO::IRQ::IRQ | IO::IRQ::SR)
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sta SPI_IO + IO::IER
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; load SR to reset
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lda SPI_IO + IO::SR
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rts
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.endproc
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;;********************************************************************************
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;; @function Stop reading/writing from/to SPI
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;; @details
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;; Disables shift register interrupts
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;; @modifies A
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;;********************************************************************************
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.proc end
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; disable SR interrupts
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lda #IO::IRQ::SR
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sta SPI_IO + IO::IER
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rts
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.endproc
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;;********************************************************************************
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;; @function Read a byte from SPI
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;; @details
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;; Reads a byte from the shift register and stores it in the SPI code buffer
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;; The first two bytes must be the size of the incumong data (LE).
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;; The spi_p:status is updated according to the current stage of the transfer.
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;; If the buffer size given in begin_read is too small too fit the incoming data,
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;; the status is set to ERROR and spi (shift register) interrupts are disabled before
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;; the first real byte is read.
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;; @modifies A,Y
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;;********************************************************************************
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.proc irq_read_byte
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lda SPI_IO + IO::SR
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bit status
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bmi @read_size1
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bvs @read_size2
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ldy recv_bytes
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sta (buffer_start),y
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inc recv_bytes
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beq @new_page
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rts
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@new_page:
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inc recv_bytes+1
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inc buffer_start+1
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rts
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@read_size1:
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sta buffer_size
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lda #spi_p::STATUS::XFER_SIZEH
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sta status
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rts
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@read_size2:
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; todo: check if the buffer is large enough:
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; low byte of buffer size in (buffer_start), high byte in buffer_size+1
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; low byte of recv buffer size in buffer_size, high byte in A
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cmp buffer_size+1
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beq @hieq
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sta buffer_size+1
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bcs @enough ; buffer larger
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bra @not_enough
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@hieq: ; high bytes are equal, check lo
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lda (buffer_start)
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cmp buffer_size
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bcs @enough
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@not_enough:
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lda #spi_p::STATUS::ERROR
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sta status
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; disable SR interrupts
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lda #IO::IRQ::SR
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sta SPI_IO + IO::IER
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rts
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@enough:
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lda #spi_p::STATUS::XFER
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sta status
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rts
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.endproc
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;;********************************************************************************
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;; @function Begin writing to spi
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;; @details
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;; - initialize variables
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;; - configure shift register to shift in under external clock
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;; - enable shift register interrupts
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;; @param ARG0-1: Start address of the buffer
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;; @param ARG2-3: Size of the buffer
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;; @todo: Use irq register handler
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;;********************************************************************************
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.proc begin_write
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stz recv_bytes
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stz recv_bytes+1
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; store address in zp
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lda #<ARG0
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sta buffer_start
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lda #>ARG1
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sta buffer_start+1
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; store size
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lda #<ARG2
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sta buffer_size
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lda #>ARG3
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sta buffer_size+1
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; load irq handler
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lda #<irq_read_byte
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sta irq_handler
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lda #>irq_read_byte
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sta irq_handler+1
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; set Shift register to shift out under external clock on CB1
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MaskedWrite SPI_IO+IO::ACR, #IO::ACR::SR_SOUT_PHIE, #IO::ACR_MASK::SR
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; enable SR interrupts
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lda #(IO::IRQ::IRQ | IO::IRQ::SR)
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sta SPI_IO + IO::IER
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; write the first byte
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@write_size1:
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lda buffer_size
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sta SPI_IO+IO::SR
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lda #spi_p::STATUS::XFER_SIZEH
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sta status
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rts
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rts
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.endproc
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;;;********************************************************************************
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;;; @function Write a byte
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;;; @details
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;;; Write a byte to the spi shift reister
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;;; @modifies A,Y
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;;;********************************************************************************
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;.proc irq_write_byte
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; ldy sent_bytes
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; lda (buffer_start),y
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; sta SPI_IO + IO::SR
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; inc sent_bytes
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; beq @new_page
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; rts
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;@new_page:
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; inc sent_bytes+1
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; inc buffer_start+1
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; rts
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;.endproc
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;;********************************************************************************
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;; @function Write a byte to SPI
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;; @details
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;; Write a byte from the buffer to the (spi) shift register.
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;; The first two bytes are the size of the data (LE).
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;; The spi_p:status is updated according to the current stage of the transfer.
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;; @modifies A,Y
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;;********************************************************************************
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.proc irq_write_byte
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bit status
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bvs @write_size2 ; bit 6 set -> XFER_SIZEH
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ldy sent_bytes
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lda (buffer_start),y
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sta SPI_IO + IO::SR
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inc sent_bytes
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beq @new_page
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rts
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@new_page:
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inc sent_bytes+1
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inc buffer_start+1
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rts
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@write_size2:
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lda buffer_size+1
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sta SPI_IO+IO::SR
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lda #spi_p::STATUS::XFER
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sta status
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rts
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.endproc
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