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
To Next Page
Loading...
