Renesas rl78 User Manual

RL78/G1A

CHAPTER 11 A/D CONVERTER

R01UH0305EJ0200 Rev.2.00

390

Jul 04, 2013

11.8 SNOOZE Mode Function

In the SNOOZE mode, A/D conversion is triggered by inputting a hardware trigger in the STOP mode. Normally, A/D

conversion is stopped while in the STOP mode, but, by using the SNOOZE mode function, A/D conversion can be

performed without operating the CPU. This is effective for reducing the operating current.

If the A/D conversion result range is specified using the ADUL and ADLL registers, A/D conversion results can be

judged at a certain interval of time in SNOOZE mode. Using this function enables power supply voltage monitoring and

input key judgment based on A/D inputs.

In the SNOOZE mode, only the following two conversion modes can be used:
• Hardware trigger wait mode (select mode, one-shot conversion mode)
• Hardware trigger wait mode (scan mode, one-shot conversion mode)

Caution The SNOOZE mode can only be specified when the high-speed on-chip oscillator clock is selected

for f

CLK

Figure 11-34. Block Diagram When Using SNOOZE Mode Function

Real-time clock (RTC),
12-bit Interval timer

Hardware trigger

input

Clock request signal

(internal signal)

High-speed on-chip

oscillator clock

A/D converter

Clock generator

A/D conversion end

interrupt request

signal

Note 1

(INTAD)

When using the SNOOZE mode function, the initial setting of each register is specified before switching to the STOP

mode. (For details about these settings, see 11.7.3 Setting up hardware trigger wait mode

Note 2

.) Just before move to

STOP mode, bit 2 (AWC) of A/D converter mode register 2 (ADM2) is set to 1. After the initial settings are specified, bit 0

(ADCE) of A/D converter mode register 0 (ADM0) is set to 1.

If a hardware trigger is input after switching to the STOP mode, the high-speed on-chip oscillator clock is supplied to

the A/D converter. After supplying this clock, the system automatically counts up to the A/D power supply stabilization

wait time, and then A/D conversion starts.

The SNOOZE mode operation after A/D conversion ends differs depending on whether an interrupt signal is

generated

Note 1

Notes 1. Depending on the setting of the A/D conversion result comparison function (ADRCK bit, ADUL/ADLL

2. Be sure to set the ADM1 register to E2H or E3H.

Remark The hardware trigger is INTRTC or INTIT.

Specify the hardware trigger by using the A/D Converter Mode Register 1 (ADM1).