
7703 GROUP
7702/7703 Group User’s Manual
20–8
20.4 Functional description
20.4.4 Serial I/O
The M37703’s UART1 can be used only in the clock asynchronous serial I/O mode, UART mode. It cannot
be used in the clock synchronous serial I/O mode. Do not set the serial I/O mode select bits (bits 2 to 0
at address 3816) to “0012” to select the clock synchronous serial I/O mode.
Figure 20.4.4 shows the structure of the UART1 transmit/receive mode register.
(1) CLK1 pin
The M37703 does not have the CLK1 pin. Set the internal/external clock select bit (bit 3 at address
3816) to “0” to select the internal clock.
Fig. 20.4.4 Structure of UART1 transmit/receive mode register
b7
b6
b5
b4
b3
b2
b1
b0
Bit
4
2
1
0
Bit name
At reset
0
RW
Functions
b2 b1 b0
3
7
6
5
RW
0
Serial I/O mode select bits
0 0 0: Serial I/O disabled
(P8 functions as a programmable
I/O port.)
0 0 1: Not selected
0 1 0: Not selected
0 1 1: Not selected
1 0 0: UART mode
(Transfer data length = 7 bits)
1 0 1: UART mode
(Transfer data length = 8 bits)
1 1 0: UART mode
(Transfer data length = 9 bits)
1 1 1: Not selected
Sleep select bit
(Valid in UART mode) (Note)
Parity enable bit
(Valid in UART mode) (Note)
Odd/Even parity select bit
(Valid in UART mode when
parity enable bit is “1”) (Note)
Stop bit length select bit
(Valid in UART mode) (Note)
UART1 transmit/receive mode register (Address 3816)
Note: Bits 4 to 6 are ignored in the clock synchronous serial I/O mode. (They may be either “0”
or “1.”) Additionally, fix bit 7 to “0.”
0 : Odd parity
1 : Even parity
0 : Parity disabled
1 : Parity enabled
0 : Sleep mode cleared (ignored)
1 : Sleep mode selected
0 : One stop bit
1 : Two stop bits
0
Fix these bits to “0”. (To select internal clock.)