
7470/7471/7477/7478 GROUP USER’S MANUAL
1-122
HARDWARE
1.13 Serial I/O
[UART transmit setting method]
1 Clear the Serial I/O transmit interrupt enable bit (bit 6 of Interrupt control register 1) to “0.”
2 When selecting the internal clock, set the BRG value.
3 Set the Serial I/O control register according to Table 1.13B.5.
4 Set the data format according to Table 1.13B.6.
5 When using a Serial I/O transmit interrupt
[1] Clear the Serial I/O transmit interrupt request bit (bit 6 of Interrupt request register 1) to “0.”
Note: When the ordinary port is switched over to the Serial I/O port, the Serial I/O transmit
interrupt request may be set to “1.” Clear the Serial I/O transmit interrupt request bit
to “0” after one instruction or more after switching the ordinary port over to the Serial
I/O port.
[2] Set the Serial I/O transmit interrupt enable bit to “1.”
6 Write transmit data into the Transmit buffer register.
Table 1.13B.5 UART transmit setting
Register to be used
Item
BRG count source selection
Synchronous clock selection
SRDY
signal output selection
Transmit interrupt request selection
Transmit enable selection
Receive enable selection
Clock asynchronous selection
Serial I/O enable selection
f (XIN)/4 or f(XCIN)/4
f (XIN)/16 or f(XCIN)/16
BRG output divided by 16
External clock input divided by 16
Transmit buffer empty
When the transmit shift operation is completed
Transmit enable
Disable (Half-duplex data communication)
Enable (Full-duplex data communication)
Clock asynchronization
P14 to P17 function as Serial I/O pins (Note 2)
Serial I/O control register
(SIOCON: Address 00E216)
bit
b0
b1
b2
b3
b4
b5
b6
b7
setting value
0
1
0
1
(Note 1)
0
1
0
1
0
1
Notes 1: When the UART is selected, this bit does not function.
2: When the internal clock is selected, the P16/SCLK pin can be used as port P16.
Table 1.13B.6 Set value of UART control register
Serial I/O data transfer format
1ST-8DATA-1SP
1ST-7DATA-1SP
1ST-8DATA-1PA-1SP
1ST-7DATA-1PA-1SP
1ST-8DATA-2SP
1ST-7DATA-2SP
1ST-8DATA-1PA-2SP
1ST-7DATA-1PA-2SP
UART control register (UARTCON: Address 00E316)
b3
0
1
b2
–
Selection
(Note)
_
Selection
(Note)
b1
0
1
0
1
b0
0
1
0
1
0
1
0
1
Note: 0: Even parity
1: Odd parity