/
spi.asm
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/
spi.asm
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;;; SPI
spiinit: lda #0x01 ; CPOL=0 and CPHA=1, which is
sta SPICONTROL ; needed by the DS1305
lda #0x02 ; div=2, which is E by 4
sta SPIDIV
lda #0xff ; "disable" the SS outputs
sta SPISS
rts
;;; SPI low level routines
spistart: sta SPISS
nop
rts
spistop: lda #0xff ; deassert chip select
sta SPISS
nop
rts
; spiwrite - send the byte in b
spiwrite: stb SPIDATAOUT
writeloop: tst SPISTATUS
bpl writeloop
rts
; spiwriteblock - sends y bytes from x
spiwriteblock: ldb ,x+
stb SPIDATAOUT
writeblockloop: tst SPISTATUS
bpl writeblockloop
leay -1,y
bne spiwriteblock
rts
; spiread - read the next spi byte into b
spiread: clr SPIDATAOUT
readloop: tst SPISTATUS
bpl readloop
ldb SPIDATAIN
rts
; spireadblock - read y bytes into the buffer starting at x
spireadblock: clr SPIDATAOUT
readblockloop: tst SPISTATUS
bpl readblockloop
ldb SPIDATAIN
stb ,x+
leay -1,y
bne spireadblock
rts