¡ Semiconductor
Control Words
There are two types of control word.
1. Mode instruction (setting of function)
2. Command (setting of operation)
MSM82C51A-2RS/GS/JS
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.
D
7
S
1
D
6
S
1
D
5
EP
D
4
PEN
D
3
L
2
D
2
L
1
D
1
B
2
D
0
B
1
Baud Rate Factor
0
0
Refer to
Fig. 3
SYNC
1
0
1
¥
0
1
16
¥
1
1
64
¥
Charactor Length
0
0
5 bits
1
0
6 bits
0
1
7 bits
1
1
8 bits
Parity Check
0
0
Disable
1
0
Odd
Parity
0
1
Disable
1
1
Even
Parity
Stop bit Length
0
0
Inhabit
1
0
1 bit
0
1
1.5 bits
1
1
2 bits
Fig. 2 Bit Configuration of Mode Instruction (Asynchronous)
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