4513 datasheet(162/210 Pages) RENESAS

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APPLICATION

2-59

4513/4514 Group User’s Manual

2.9 RAM back-up

2.9.1 RAM back-up mode

The system enters RAM back-up mode when the POF instruction is executed after the EPOF instruction

is executed. Table 2.9.1 shows the function and state retained at RAM back-up mode. Also, Table 2.9.2

shows the return source from this state.

(1)

RAM back-up mode

As oscillation stops with RAM, the state of reset circuit retained, current dissipation can be reduced

without losing the contents of RAM.

Function

Program counter (PC), registers A, B,

carry flag (CY), stack pointer (SP) (Note 2)

Contents of RAM

Port level

Timer control register W1

Timer control registers W2 to W4. W6

Clock control register MR

Interrupt control registers V1, V2

Interrupt control registers I1, I2

Timer 1 function

Timer 2 function

Timer 3 function

Timer 4 function

A-D function

A-D control registers Q1, Q2

Voltage comparator function

Voltage comparator control register Q3

Serial I/O function

Serial I/O mode register J1

RAM back-up

(Note 3)

O (Note 5)

Table 2.9.1 Functions and states retained at RAM back-up mode

Function

Pull-up control register PU0

Key-on wakeup control register K0

Direction register FR0

External 0 interrupt request flag (EXF0)

External 1 interrupt request flag (EXF1)

Timer 1 interrupt request flag (T1F)

Timer 2 interrupt request flag (T2F)

Timer 3 interrupt request flag (T3F)

Timer 4 interrupt request flag (T4F)

Watchdog timer flags (WDF1, WDF2)

Watchdog timer enable flag (WEF)

16-bit timer (WDT)

A-D conversion completion flag (ADF)

Serial I/O transmit/receive completion flag

(SIOF)

Interrupt enable flag (INTE)

RAM back-up

(Note 3)

! (Note 4)

Notes 1: “O” represents that the function can be retained, and “!” represents that the function is initialized.

Registers and flags other than the above are undefined at RAM back-up, and set an initial value

after returning.

2: The stack pointer (SP) points the level of the stack register and is initialized to “7” at RAM back-

up.

3: The state of the timer is undefined.

4: Initialize the watchdog timer with the WRST instruction, and then execute the POF instruction.

5: The state is retained when the voltage comparator function is selected with the voltage comparator

control register Q3.

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