M38203M4 Datasheet, PDF (189/344 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.5 Serial I/O1
2.5 Serial I/O1
2.5.1 Explanation of operations
As a serial I/O1, it is possible to select either the clock synchronous serial I/O1 mode or the clock
asynchronous serial I/O1 (UART) mode. This section describes operations in both the clock synchronous
mode and the clock asynchronous (UART) mode. When serial I/O1 is actually used, refer to “2.5.4 Reg-
ister setting example.”
(1) Clock synchronous serial I/O1 mode
In the clock synchronous mode, 8 shift clocks generated in the clock control circuit are used as
synchronizing clocks for transfer. In synchronization with these shift clocks, the transmit operation on
the transmitter and the receive operation on the receiver are simultaneously executed.
The transmitter transmits each 1-bit data from the P45/TxD pin in synchronization with the falling of
the shift clocks.
The receiver receives each 1-bit data from the P44/RxD pin in synchronization with the rising of the
shift clocks.
Figure 2.5.1 shows an external connection example in the clock synchronous mode.
3820 group Œ
3820 group 
XIN
8
Receive buffer register
Receive shift register
RxD
1/4
Clock control circuit
BRG
1/(n+1) 1/4
SCLK
TxD
SCLK
8
Transmit buffer register
Transmit shift register
Clock control circuit
Transmit shift register
TxD
Transmit buffer register
8
RxD _{Receive shift register}
Receive buffer register
8
Internal clock is selected
External clock is selected
Fig. 2.5.1 External connection example in clock synchronous mode
3820 GROUP USER’S MANUAL
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