PC87570 datasheet(80/168 Pages) NSC

80 / 168 page

Power Mode Control (PMC)

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8.4

POWER MODE CONTROL REGISTER (PMCR)

The PMCR Register is a byte-wide, read/write register that

enables you to switch from Active to Idle mode. In addition,

it controls the operation of the HFCG in Idle mode by en-

abling or disabling it. The PC87570 enters Idle mode after

execution of a WAIT instruction. The PMCR Register must

be set before executing the WAIT instruction.

Upon reset, the non-reserved bits of PMCR are cleared.

Bit 1 - Disable High Frequency Clock Generator (DHF)

0: HFCG remains enabled after entering Idle mode;

waking up to Active mode clears this bit

1: HFCG disabled only after WAIT instruction is exe-

cuted and Idle mode is entered

Bit 2 - IDLE

0: PC87570 remains in Active mode after WAIT in-

struction is executed

1: PC87570 can enter Idle mode, depending on set-

ting of EIM bit; waking up to Active mode clears

this bit

Bit 5 - Enable Idle Mode (EIM)

0: Idle mode not enabled

1: Active to Idle mode switch enabled, performed by

setting IDLE bit and executing a WAIT instruction.

8.5

USAGE HINTS

The hints below apply when you enter Idle mode and dis-

able the HFCG.

1. When disabling HFCG in Idle mode, a frequency clock

may be generated that differs from the selected setting,

due to temperature variations in your working environ-

ment. For details, refer to “tCLKINTwk” on page 138. To

avoid any failures that may result from waking up to a

higher frequency than zone 0 of the External Memory

can handle, follow the procedures exactly.

Before entering Idle mode, configure SZCFG0 for an ad-

ditional Wait clock cycle (see the BIU, Section 3.5.3 on

page 45, for details on SZCFG0 configuration).

2. After waking up from Idle mode, wait 0.5 seconds before

returning to your previous SZCFG0 configuration.

Active

Idle

Power Off

Turn Off Power

PMCR.EIM=1

Turn On Power

Hardware Event

Reset

Figure 8-1. Power Modes and Transitions

PMCR.IDLE=1

and WAIT

Reserved

EIM

Reserved IDLE

DHF

Res

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