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Serial I/O2
2.6.7 Precautions for Serial I/O2
(1) Clock
(a) Using internal clock
After setting the synchronous clock to an internal clock, clear the serial I/O interrupt request bit
before performing a normal serial I/O transfer or a serial I/O automatic transfer.
(b) Using external clock
After inputting “H” level to the external clock input pin, clear the serial I/O interrupt request bit before
performing a normal serial I/O transfer or a serial I/O automatic transfer.
(2) Using Serial I/O2 interrupt
Clear bit 3 of the interrupt control register to “0” by software before enabling interrupts.
(3) State of SOUT2 pin
The SOUT2 pin control bit of the serial I/O2 control register 2 can be used to select the SOUT2 pin state
for non-transfer periods. Either output active or high-impedance can be selected. However, when
using an external synchronous clock, set the SOUT2 pin control bit to “1” while the serial I/O2 clock
input is in “H” level (after transfer completion) in order to put the SOUT2 pin in the high-impedance state.
(4) Serial I/O initialization bit
To terminate a serial transfer while transferring, set “0” to the serial I/O initialization bit of the serial
I/O2 control register 1.
When “1” is written to the serial I/O initialization bit, Serial I/O2 is enabled, however, each register is
not initialized. The value of each register needs to be set by software.
(5) Handshake signal
(a) SBUSY2 input signal
Input “H” level to the SBUSY2 input and “L” level to the SBUSY2 input in the initial state. When using the
external synchronous clock, switch the input level to the SBUSY2 input and the SBUSY2 input while the
serial I/O2 clock input is in “H” level.
(b) SRDY2 input/output signal
When using the internal synchronous clock, input “L” level to the SRDY2 input and “H” level to the
SRDY2 input in the initial state.
(6) In 8-bit serial I/O mode
When the external synchronous clock is used, the contents of the serial I/O2 register are being shifted
continually while the transfer clock is input to the serial I/O2 clock pin. At this time, the clock must be
controlled externally.