Epson PX-8 Technical Manual page 126

REV.-A
2.11.2 RS-232C Interface Circuit Operations
The base transmit/receive clock signal is supplied from GAH40M and data are converted from
parallel to serial and vice versa at the same rate as the base signal; one sixteenth or one sixty-
fourth of the base rate can be selected using the mode instruction register. The baud rate genera-
tor in GAH40M needs to be set to the desired rate before an RS-232C operation is initiated. The
data read/write and interrupt are controlled by the main CPU and via the GAH40M.
2.11.2.1 Baud rate Generator Setting
The baud rate generator can be set by modifying bits 4 through 7 of the register, I/O address 00,
through a write from the main CPU:
Table 2-20 Baud rate Generator Settings
B't 7
I
r-Bit 6
Bit 5
rBit4
B B B B
Baud 8251 Baud 8251
R R R R
TXC
Rate x 1/16 Rate x 1/64
RXC
G G G G
(8251 clock)
3
2 1
0
TX RX TX RX
0 0 0 0 1.74545K 1.74545K 110 110
- - - -
0 0
0
1 2.4K
2.4K 150 150
- -
- -
0 0
1
0 4.8K 4.8K 300 300
- - - - -
0 0 1 1 9.6K 9.6K
600 600 150 150
0 1 0 0 19.2K 19.2K 1200 1200
300 300
0 1 0 1 38.4K
38.4K
2400
2400 600 600
0 1 1 0 76.8K 76.8K 4800 4800 1200 1200
0 1 1 1 153.6K 153.6K
9600 9600
2400 2400
1 0 0 0 19.2K 1.2K 1200 75
- - - -
1 0 0 1 1.2K 19.2K 75 1200
- - - -
1 0 1 0 307.2K 307.2K 19.2K
19.2K
4800 4800
1 1 0 0 3.2K 3.2K 200 200
- - - -
*
For asynchronous transmission/reception (start-stop bit system), the transmit/receive clock
rate is internally obtained by dividing the base signal down to one sixteenth or one sixtyfourth.
2.-102