Renesas rl78 User Manual

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

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

SDR00

SCK00 pin

CPU operation status

STOP mode

SNOOZE mode

Normal operation

SI00 pin

Clock request signal

(internal signal)

INTCSI00

TSF00

Receive data 2

ST00

Shift

Receive data 1

Receive data 2

Reception & shift operation

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).

m = 0; p = 00

<R>