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RL78/G1A CHAPTER 12 SERIAL ARRAY UNIT
R01UH0305EJ0200 Rev.2.00 495
Jul 04, 2013
12.5.7 SNOOZE mode function
SNOOZE mode makes CSI operate reception by SCKp pin input detection while the STOP mode. Normally CSI stops
communication in the STOP mode. But, using the SNOOZE mode makes reception CSI operate unless the CPU
operation by detecting SCKp pin input. Only CSIs00 can be specified for asynchronous reception.
When using the CSI in SNOOZE mode, make the following setting before switching to the STOP mode (see Figure 12-
72 Flowchart of SNOOZE Mode Operation (Once Startup) and Figure 12-74 Flowchart of SNOOZE Mode
Operation (Continuous Startup)).
• When using the SNOOZE mode function, set the SWCm bit of serial standby control register m (SSCm) to 1 just
before switching to the STOP mode. After the initial setting has been completed, set the SSm1 bit of serial channel start
register m (SSm) to 1.
After a transition to the STOP mode, the CSI starts reception operations upon detection of an edge of the SCKp pin.
Cautions 1. The SNOOZE mode can only be specified when the high-speed on-chip oscillator clock is selected
for f
CLK.
2. The maximum transfer rate when using CSIp in the SNOOZE mode is 1 Mbps.
(1) SNOOZE mode operation (once startup)
Figure 12-70. Timing Chart of SNOOZE Mode Operation (Once Startup) (Type 1: DAPmn = 0, CKPmn = 0)
SS00
SE00
SWC0
SSEC0 L
SDR00
SCK00 pin
CPU operation status
STOP mode
SNOOZE modeNormal operation Normal operation
SI00 pin
Clock request signal
(internal signal)
INTCSI00
TSF00
Receive data 2
ST00
Shift
register 00
Receive data 1
Receive data 1
Receive data 2
Reception & shift operation
Reception & shift operation
Data reception Data reception
Read
Note
<3>
<4>
<11>
<9>
<10>
<8>
<7>
<2>
<5><6>
<1>
Note Only read received data while SWCm = 1 and before the next edge of the SCKp pin input is detected.
Cautions 1. Before switching to the SNOOZE mode or after reception operation in the SNOOZE mode
finishes, set the STm0 bit to 1 (clear the SEm0 bit, and stop the operation).
And after completion the receive operation, also clearing SWCm bit to 0 (SNOOZE mode
release).
2. When SWCm = 1, BFFm1, OVFm1 flags are not operation.
Remarks 1. <1> to <11> in the figure correspond to <1> to <11> in Figure 12-71 Flowchart of SNOOZE Mode
Operation (Once Startup).
2. m = 0; p = 00
<R>
<R>