¡ Semiconductor
MSM82C51A-2RS/GS/JS
Control Words
There are two types of control word.
1. Mode instruction (setting of function)
2. Command (setting of operation)
1) Mode Instruction
Mode instruction is used for setting the function of the MSM82C51A-2. Mode instruction
will be in “wait for write” at either internal reset or external reset. That is, the writing of a
control word after resetting will be recognized as a “mode instruction.”
Items set by mode instruction are as follows:
•
•
•
•
•
•
•
Synchronous/asynchronous mode
Stop bit length (asynchronous mode)
Character length
Parity bit
Baud rate factor (asynchronous mode)
Internal/external synchronization (synchronous mode)
Number of synchronous characters (Synchronous mode)
The bit configuration of mode instruction is shown in Figures 2 and 3. In the case of
synchronous mode, it is necessary to write one-or two byte sync characters.
If sync characters were written, a function will be set because the writing of sync characters
constitutes part of mode instruction.
D7
S1
D6
S1
D5
EP
D4
D3
L2
D2
L1
D1
B2
D0
B1
PEN
Baud Rate Factor
0
0
1
0
0
1
1
1
Refer to
Fig. 3
SYNC
1 ¥
16 ¥
64 ¥
Charactor Length
0
0
1
0
0
1
1
1
5 bits
6 bits
7 bits
8 bits
Parity Check
0
0
1
0
0
1
1
1
Odd
Parity
Even
Parity
Disable
Disable
Stop bit Length
0
0
1
0
0
1
1
1
Inhabit
1 bit
1.5 bits
2 bits
Fig. 2 Bit Configuration of Mode Instruction (Asynchronous)
5/26
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