herman@ti-csl.UUCP (02/24/87)
in article <1260@beta.UUCP>, dzzr@beta.UUCP (Douglas J Roberts) says: > > Does anybody know the commands for the 8251 USART? > I would like to tell the USART in my Z-80 CPM machine to > send serial data with 1 start bit, 7 data bits, 1 parity bit, and > one stop bit. > > The initialization routine in my bios sends 0CEH to the serial status > port which sets the UART to 2 stop bits, 16xclock, 8 data bits, no parity. > > If anybody knows the other control bytes, mucho appreciado! > > -- > Douglas J. Roberts, dzzr@lanl.gov > Los Alamos National Laboratory > Box 1663, F602 > Los Alamos, N. M. 87544 Mode format - async mode 0-1 Clock rate: 00 = sync mode, 01 = 1x, 10 = 16x, 11 = 64x 2-3 Char length: 00 = 5, 01 = 6, 10 = 7, 11 = 8 bits 4 Parity enable: 0 = disabled, 1 = enabled 5 Parity: 0 = odd, 1 = even 6-7 Stop bits: 00 = invalid, 01 = 1, 10 = 1.5, 11 = 2 Command instruction 0 Transmit enable: 1 = enable 1 Data Terminal Ready: 1 = ~DTR is forced low 2 Receive enable: 1 = enable 3 Send break character: 1 = TxD "low", 0 = normal operation 4 Error reset: 1 = Reset PE, OE and FE flags 5 Request to send: 1 = ~RTS is forced low 6 Internal reset: 1 = enter mode instruction format 7 Enter HUNT mode: 1 = enable search for sync chars Status byte 0 TxRDY: 1 = Transmitter ready for next character 1 RxRDY: 1 = Receiver ready - character waiting 2 TxEMPTY: 1 = Transmit buffer empty 3 PE: Parity Error 4 OE: Overrun Error 5 FE: Framing Error 6 SynDet: 1 = Sync character detected 7 DSR: 1 = Data Set Ready Bit #0 is the least significant bit; #7 is the most significant bit. The mode byte for 1 start bit, 7 data bits, odd parity, and 1 stop bit would be 05Ah (which includes the 16x clock factor too). -- Herman Schuurman ARPA: herman%TI-CSL@CSNET-RELAY.ARPA Texas Instruments Inc. CSNET: herman@TI-CSL PO Box 226015 M/S 238 USENET: {ut-sally,convex!smu,texsun,rice}!ti-csl!herman Dallas, Texas 75266 VOICE: (214) 995-0845