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7.4 Clock asynchronous serial I/O (UART) mode
Table 7.4.1 lists the performance overview in the UART mode, and Table 7.4.2 lists the functions of I/O pins
in this mode.
Table 7.4.1 Performance overview in UART mode
Transfer data
Start bit
format
Character bit (Transfer data)
Parity bit
Stop bit
Transfer rate
When selecting internal clock
When selecting external clock
Error detection
Table 7.4.2 Functions of I/O pins in UART mode
Pin name
TxD
(P8
, P8
)
i
3
7
RxD
(P8
, P8
)
i
2
6
CLK
(P8
, P8
)
i
1
5
____ ____
/
(P8
, P8
)
CTS
RTS
i
i
0
4
Port P8 direction register
Internal/External clock select bit
____ ____
3
CTS/RTS select bit
: bit 2 at addresses 34
Notes 1: The TxD
pin outputs "H" level while not transmitting after selecting UARTi's operating mode.
i
2: The RxD
pin can be used as a programmable I/O port when performing only transmission.
i
3: The CLK
pin can be used as a programmable I/O port when selecting internal clock.
i
___
___
4: The CTS
/RTS
i
function (when selecting CTS function).
Item
Functions
Serial data output
Serial data input
BRGi's count source
input
____
CTS input
____
RTS output
1
: Address 14
16
2
: bit 3 at addresses 30
pin can be used as a input port when performing only reception and not using RTS
i
___
7751 Group User's Manual
7.4 Clock asynchronous serial I/O (UART) mode
1 bit
7 bits, 8 bits, or 9 bits
0 bit or 1 bit (Odd or even can be selected.)
1 bit or 2 bits
Clock of BRGi output divided by 16
Maximum 312.5 kbps
4 types (Overrun, Framing, Parity, and Summing)
Presence of error can be detected only by checking error sum flag.
Fixed
Port P8 direction register
Internal/External clock select bit
____ ____
CTS/RTS select bit
____ ____
CTS/RTS select bit = "1"
, 38
16
16
, 3C
16
16
SERIAL I/O
Functions
Method of selection
1
's corresponding bit = "0"
2
= "1"
3
= "0"
___
7–35
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