Toshiba TC9314F Manual page 42

This method works as follows. To transmit data, the data are set in the serial output data port and
SIO is performed. To receive data, the SO pin is set to input and SIO is performed. Then, the data can
be loaded to data memory from the serial input data port. Even when the serial interface is selected,
the SI pin can be controlled as an I/O port (P4-0). The I/O output pins (P4-0) can be used, for example,
as the strobe pulse pins in T-BUS.
Note 46: When set as the SI serial data input pin, set the corresponding I/O control port P4-0 bits in I/O
port 4 to "0".
(5) Monitoring serial interface operation
Use the BUSY, COUNT, and SIO flip-flop bits to check the operating state of the serial interface.
The BUSY bit is set to "1" during SIO operations. Therefore, set the control data and access the
serial data when the BUSY bit is "0".
Use the COUNT bit to determine whether data in units of 4 bits have been sent or received. When
the number of shift operations is a multiple of 4, the COUNT bit outputs "0". When not a multiple of 4,
the bit outputs "1".
The SIO flip-flop bit is set to "1" when the SCK pin clock starts.
Setting the STA bit to "1" clears both the COUNT bit and SIO flip-flop bit to "0". These two bits are
mainly used when the SCK pin is set for the external clock. The bits can be used to test whether the
external clock was input, whether serial data were sent or received, or whether operations were
normal.
(6) STA bit
With the SCK pin set for the internal clock, each time the STA bit is set to "1", the serial output
data are set to the shift register, the clock is output from the SCK pin, and shift operations begin.
At this time, the COUNT bit and the SIO flip-flop are reset to "0".
2. Serial Interface Structure
The serial interface consists of a control circuit, a shift register, and I/O ports.
Note 47: The SI pin can be used as-is as I/O port 4 (P4-0)
Note 48: The data set as the serial output data are different to the serial input data.
Note 49: When the SI pin is set to SI input, when the SCK pin is set to SCK input, and when the SO pin is
set to input, the pins are all Schmitt inputs.
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TC9314F
2003-07-03