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Task-Specific Program Code
C-15
Program Examples
Example C–10. Loopback to Verify Transmissions of Asynchronous Serial Port (echo.asm)
(Continued)
* UART initialization *
splk #0ffffh,ifr ; clear interrupts
splk #0000h,60h
out 60h, wsgr ; Set zero wait states
splk #0c080h,61h ; reset the UART by writing 0
out 61h, aspcr ; 1 stop bit, rx interrupt, input i/o
splk #0e080h,61h
out 61h,aspcr
splk #4fffh,62h
out 62h,iosr ; disable auto baud
splk #0411h, 63h ; set baud rate =1200 @ 20MHz CLKOUT1
out 63h, brd
splk #20h,imr ; enable UART interrupt
mar *,ar1
* Load data at DM300
lar ar1,#rxbuf
lar ar0, #size ; load buffer size
mar *,ar1 ; load data pointer
clrc intm
wait: clrc xf ; toggle xf bit
idle
b wait
uart: setc xf ; toggle xf bit
; Check receive flag bit in iosr
in 68h,iosr ; load input status from iosr
bit 68h,7 ; bit 8 in the data
bcnd skip,ntc ; IF DR=0 no echo, return
in *,adtr ; read and save at 300h
out *+,adtr ; echo
mar *,ar0
banz skip,ar1 ; check if size=0, and reload
lar ar1,#rxbuf
lar ar0,#size
skip: splk #0020h, ifr ; Clear interrupt in ifr!
clrc intm
ret
inpt1: ret
inpt23: ret
timer: ret
codtx: ret
codrx: ret
.end ; Assembler module end directive
; –optional