SERIAL I/O
7902 Group User’s Manual
12-24
12.3 Clock synchronous serial I/O mode
Fig. 12.3.2 Initial setting example for relevant registers when transmitting
0
UART0 transmit/receive mode register (Address 3016)
UART1 transmit/receive mode register (Address 3816)
b7
b0
Internal/External clock select bit
0: Internal clock
1: External clock
!
!!
!: It may be either “0” or “1.”
Selection of clock synchronous serial
I/O mode
UART0 transmit/receive control register 0 (Address 3416)
UART1 transmit/receive control register 0 (Address 3C16)
b7
b0
BRG count source select bits
CTS
/RTS function select bit
0: CTS function selected
1: RTS function selected
0 0 : f2
0 1 : f16
1 0 : f64
1 1 : f512
b1 b0
Transmission starts.
UART0 transmit buffer register (Address 3216)
UART1 transmit buffer register (Address 3A16)
b7
b0
Transmit data is set.
1
UART0 transmit/receive control register 1 (Address 3516)
UART1 transmit/receive control register 1 (Address 3D16)
b7
b0
Transmit enable bit
1: Transmission is enabled.
(In the case of selecting the CTS function, transmission
starts when the CTS0 pin’s input level is “L.”)
UART0 baud rate register (BRG0) (Address 3116)
UART1 baud rate register (BRG1) (Address 3916)
b7
b0
Can be set to “0016” to “FF16.”
UART0 transmit interrupt control register (Address 7116)
UART1 transmit interrupt control register (Address 7316)
b7
b0
Interrupt priority level select bits
When using interrupts, set these bits to
one of levels 1 to 7.
When disabling interrupts, set these bits
to level 0.
CTS
/RTS enable bit
0: CTS/RTS function is enabled.
1: CTS/RTS function is disabled.
CLK polarity select bit
0: At the falling edge of the transfer
clock, transmit data is output.
1: At the rising edge of the transfer
clock, transmit data is output.
Transfer format select bit
0: LSB first
1: MSB first
Serial I/O pin control register (Address AC16)
b7
b0
CTS0/RTS0 separate select bit
0: CTS0/RTS0 are used together (Note).
Note: In the clock synchronous serial I/O
mode, CTSi/RTSi separation cannot
be selected. (Refer to section “[Pre-
cautions for clock synchronous
serial I/O mode].”)
When extenal clock is selected
When internal clock is selected
1
0
CTS1/RTS1 separate select bit
0: CTS1/RTS1 are used together (Note).
TxD0/P83 switch bit
0: Functions as TxD0.
TxD1/P87 switch bit
0: Functions as TxD1.