using the Rockwell part
my initialization routine:
Code:
uartinit:
PHA
STZ COM1_STA ;write a zero to ACIA status register to reset chip
LDA #@00011110 ;ACIA control register setting for 1 stop, 8 data, 9600 baud
STA COM1_CON ;set ACIA control register
LDA #@00001001 ;no parity, no echo, no Tx IRQ, RTSB LOW, Rx IRQ enabled, DTRB LOW
STA COM1_COM ;set ACIA command register
PLA
RTS
after this code runs, the UART sets IRQB LOW. I clear it by reading the status register.
Any attempts to write to the data register causes no activity on the TXd pin.
Using an FTDI serial to usb connector
Other pins are set as follows:
RXc is not connected
XTL1 getting clock from 1.8432 X0, Its an oscillator, not just a crystal. Clock sugnal is confirmed
XTL2 not connected
CTSB is connected to ground, and to the proper pin on the FTDI
RTSB is connected to pin on FTDI. Reads LOW when probed.
DTRB connected to pin on FTDI. Reads LOW when probed
DSRB grounded, and connected to FTDI
DCDB grounded and connected to FTDI
terminal emulator set for no handshaking
Why is the transmitter not working?
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Turns out accidentally using the native rs232 voltage level ftdi part doesn't work in a 5 volt system