CHAPTER 15 SERIAL INTERFACE CHANNEL 1
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(4) Synchronization control
Busy control and strobe control are to synchronize transmission/reception data between the master device
and slave device.
By using these functions, a bit slippage in data being transmitted/received can be detected.
(a) Busy control option
Busy control is to allow a slave device to output a busy signal to the master device, so that the master
device puts serial transmission/reception into a wait state while the busy signal is active.
To use the busy control option, the following conditions must be satisfied:
Set bit 5 (ATE) of the serial operating mode register 1 (CSIM1) to 1.
Set bit 1 (BUSY1) of the automatic data transmit/receive control register (ADTC) to 1.
Figure 15-18 shows the system configuration of the master device and a slave device when the busy
control option is used.
Figure 15-18. System Configuration with Busy Control Option
SCK1
SO1
SI1
SCK1
SO1
SI1
BUSY
Master device
( PD78044F Subseries)
Slave device
The master device inputs the busy signal output by the slave device to the BUSY/P24 pin. It samples
the input busy signal in synchronization with the fall of the serial clock. Even if the busy signal becomes
active while 8-bit data is transmitted or received, transmission/reception is not put into a wait state. If
the busy signal is active at the rising edge of the serial clock two clocks after transmission or reception
of 8-bit data has been completed, the busy signal becomes valid. After that, transmission or reception
is put into a wait state while the busy signal is active.
The active level of the busy signal is specified by bit 0 (BUSY0) of ADTC, as follows:
BUSY0 = 0: Active high
BUSY0 = 1: Active low
When using the busy control option, select the internal clock as the serial clock. Busy control cannot
be executed with the external clock.
Figure 15-19 shows the operation timings when using the busy control option.
Caution
Busy control cannot be executed when the interval time is controlled by using the
automatic data transmit/receive interval specify register (ADTI).
If an attempt is made to execute both control operations at the same time, busy control
is invalid.