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(b) Busy & strobe control option
Figure 17-20. Operation Timings when Using Busy & Strobe Control Option (BUSY0 = 0)
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BUSY
CSIIF1
CHAPTER 17 SERIAL INTERFACE CHANNEL 1
Strobe control is a function to synchronize data transmission/reception between the master and slave
devices. The master device outputs the strobe signal from the STB/P23 pin when 8-bit transmission/
receptixon has been completed. By this signal, the slave device can determine the timing of the end of data
transmission.
Therefore, synchronization is established even if a bit shift occurs because noise is
superimposed on the serial clock, and transmission of the next byte is not affected by the bit shift.
To use the strobe control option, the following conditions must be satisfied:
• Bit 5 (ATE) of the serial operation mode register 1 (CSIM1) is set to 1.
• Bit 2 (STRB) of the automatic data transmission/reception control register (ADTC) is set to 1.
Usually, the busy control and strobe control options are simultaneously used as handshake signals. In this
case, the strobe signal is output from the STB/P23 pin, and the BUSY/P24 pin is sampled, and transmission/
reception can be kept waiting while the busy signal is input.
When the strobe control option is not used, the P23/STB pin can be used as a normal I/O port pin.
Figure 17-20 shows the operation timing when the busy & strobe control options are used.
When the strobe control option is used, the interrupt request flag (CSIIF1) that is set on completion of
transmission/reception is set after the strobe signal is output.
SCK1
D7
D6 D5 D4 D3 D2 D1 D0
SO1
D7 D6 D5 D4 D3 D2 D1 D0
SI1
STB
TRF
Caution When TRF is cleared, the SO1 pin becomes low.
Remark CSIIF1 : Interrupt request flag
TRF
: Bit 3 of the automatic data transmit/receive control register (ADTC)
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
Busy Input Clear
Busy Input Valid
441
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