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CHAPTER 17 SERIAL INTERFACE CHANNEL 1
Figure 17-20. Busy Signal and Wait Release (when BUSY0 = 0)
SCK1
D7
SO1
SI1
D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
BUSY
(active high)
1.5 clock (min.)
Busy input released
Busy input valid
Wait
If made inactive
immediately after
sampled
(b) Busy & strobe control option
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/
reception 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 transmit/receive 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 17-21 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.