Rev.1.01
Jan 25, 2005
page 51 of 114
REJ03B0131-0101Z
3804 Group (Spec. H)
2. Notes when selecting clock asynchronous serial I/O
2.1 Stop of transmission operation
q Note
Clear the transmit enable bit to “0” (transmit disabled). The trans-
mission operation does not stop by clearing the serial I/O3 enable
bit to “0”.
q Reason
Since transmission is not stopped and the transmission circuit is
not initialized even if only the serial I/O3 enable bit is cleared to “0”
(serial I/O disabled), the internal transmission is running (in this
case, since pins TxD3, RxD3, SCLK3, and SRDY3 function as I/O
ports, the transmission data is not output). When data is written to
the transmit buffer register in this state, data starts to be shifted to
the transmit shift register. When the serial I/O3 enable bit is set to
“1” at this time, the data during internally shifting is output to the
TxD3 pin and an operation failure occurs.
2.2 Stop of receive operation
q Note
Clear the receive enable bit to “0” (receive disabled).
2.3 Stop of transmit/receive operation
q Note 1 (only transmission operation is stopped)
Clear the transmit enable bit to “0” (transmit disabled). The trans-
mission operation does not stop by clearing the serial I/O3 enable
bit to “0”.
q Reason
Since transmission is not stopped and the transmission circuit is
not initialized even if only the serial I/O3 enable bit is cleared to “0”
(serial I/O disabled), the internal transmission is running (in this
case, since pins TxD3, RxD3, SCLK3, and SRDY3 function as I/O
ports, the transmission data is not output). When data is written to
the transmit buffer register in this state, data starts to be shifted to
the transmit shift register. When the serial I/O3 enable bit is set to
“1” at this time, the data during internally shifting is output to the
TxD3 pin and an operation failure occurs.
q Note 2 (only receive operation is stopped)
Clear the receive enable bit to “0” (receive disabled).
s Notes concerning serial I/O3
1. Notes when selecting clock synchronous serial I/O
1.1 Stop of transmission operation
q Note
Clear the serial I/O3 enable bit and the transmit enable bit to “0”
(serial I/O and transmit disabled).
q Reason
Since transmission is not stopped and the transmission circuit is
not initialized even if only the serial I/O3 enable bit is cleared to “0”
(serial I/O disabled), the internal transmission is running (in this
case, since pins TxD3, RxD3, SCLK3, and SRDY3 function as I/O
ports, the transmission data is not output). When data is written to
the transmit buffer register in this state, data starts to be shifted to
the transmit shift register. When the serial I/O enable bit is set to
“1” at this time, the data during internally shifting is output to the
TxD3 pin and an operation failure occurs.
1.2 Stop of receive operation
q Note
Clear the receive enable bit to “0” (receive disabled), or clear the
serial I/O3 enable bit to “0” (serial I/O disabled).
1.3 Stop of transmit/receive operation
q Note
Clear both the transmit enable bit and receive enable bit to “0”
(transmit and receive disabled).
(when data is transmitted and received in the clock synchronous
serial I/O mode, any one of data transmission and reception can-
not be stopped.)
q Reason
In the clock synchronous serial I/O mode, the same clock is used
for transmission and reception. If any one of transmission and re-
ception is disabled, a bit error occurs because transmission and
reception cannot be synchronized.
In this mode, the clock circuit of the transmission circuit also oper-
ates for data reception. Accordingly, the transmission circuit does
not stop by clearing only the transmit enable bit to “0” (transmit
disabled). Also, the transmission circuit is not initialized by clear-
ing the serial I/O3 enable bit to “0” (serial I/O disabled) (refer to
1.1).