ACT apricot - Page 170

SERIAL INTERFACE
To receive and transmit data in the asynchronous mode,
the following conditions have to be determined:
1. The transmit and receive baud rates.
2. The character length.
3.
The number of stop bits in the transmit character. ( 1
stop
bit is always expected in the receive data).
4. The sense of the parity, if any.
5. The interrupt mode.
6. The line protocol.
Baud Rate Selection. The clock source for determining the
transmit and receive baud ratesis selected according to the
programmed state of the RTS and DTR bits of Write
Register 5 in channel B, as follows.
RTS
DTR Rx Clock Tx Clock
a a
OUTI (TMR) OUT2 (TMR)
0
1 External Clock External Clock
1
a
OUT2 (TMR) OUT2 (TMR)
1 1
OV OV
Write Register 4. This register determines, the number of
stop bits
in the transmit data, the sense of the parity (if any)
in the transmit data and the expected parity in the receive
data,
the multiplier applied to both the transmit and receive
input clock rates prior to setting the baud rates.
07
DO
I 0 11 I x I x 1
03
1
02
1 01 ( DO I Write Register 4
I I
x 0 Par ty Off
o 1 Par ty Odd
1 1 Par ty Even
o 1 1 stop bit
1 0 1.5 stop bits
1 1 2 stop bits
---- x16 clock rate