SERIAL I/O
11.2 Block description
(1) Serial I/O mode select bits (bits 0 to 2)
These bits select a UARTi’s operating mode.
(2) Internal/External clock select bit (bit 3)
ꢀ Clock synchronous serial I/O mode
By clearing this bit to “0” in order to select an internal clock, the clock which is selected with the
BRG count source select bits (bits 0 and 1 at addresses 3416, 3C16 and B416) becomes the count
source of the BRGi. (Refer to section “11.2.6 UARTi baud rate register (BRGi).”) The BRGi’s
output divided by 2 becomes the transfer clock. Additionally, the transfer clock is output from the
CLK pin.
i
By setting this bit to “1” in order to select an external clock, the clock input to the CLK pin
i
becomes the transfer clock.
ꢀ UART mode
By clearing this bit to “0” in order to select an internal clock, the clock which is selected with the
BRG count source select bits (bits 0 and 1 at addresses 3416, 3C16 and B416) becomes the count
source of the BRGi. (Refer to section “11.2.6 UARTi baud rate register (BRGi).”) Then, the CLK
i
pin functions as a programmable I/O port pin.
By setting this bit to “1” in order to select an external clock, the clock input to the CLK
becomes the count source of BRGi.
i
pin
Always in the UART mode, the BRGi’s output divided by 16 becomes the transfer clock.
(3) Stop bit length select bit, Odd/Even parity select bit, Parity enable bit (bits 4 to 6)
Refer to section “11.4.2 Transfer data format.”
(4) Sleep select bit (bit 7)
Refer to section “11.4.8 Sleep mode.”
7905 Group User’s Manual Rev.1.0
11-5
RENESAS [ RENESAS TECHNOLOGY CORP ]
