UPD17217GT datasheet(46/84 Pages) NEC

46 / 84 page

µPD17215, 17216, 17217, 17218

STANDBY FUNCTIONS

µPD17215 is provided with HALT and STOP modes as standby functions. By using the standby function, current

dissipation can be reduced.

In the HALT mode, the program is not executed, but the system clock fx is not stopped.

This mode is main-

tained, until the HALT mode release condition is satisfied.

In the STOP mode, the system clock is stopped and program execution is stopped. This mode is maintained, until the

STOP mode release condition is satisfied.

The HALT mode is set, when the HALT instruction has been executed. The STOP mode is set, when the STOP

instruction has been executed.

8.1

HALT Mode

In this mode, program execution is temporarily stopped, with the main clock continuing oscillating, to reduce current

dissipation. Use the HALT instruction to set the HALT mode.

The HALT mode releasing condition can be specified by the operand for the HALT instruction, as shown in Table 8-1.

After the HALT mode has been released, the operation is performed as shown in Table 8-1 and Figure 8-2.

Caution:

Do not execute an instruction that clears the interrupt request flag (IRQxxx) for which the interrupt

enable flag (IPxxx) is set immediately before the HALT 8H instruction; otherwise, the HALT mode

may not be set.

Table 8-1

HALT Mode Releasing Conditions

Operand Value

Releasing Conditions

0010B (02H)

When interrupt request (IRQTM) occurs for 8-bit timer

<1> When interrupt request (IRQTM, IRQWTM, or IRQ), whose interrupt enable flag (IPTM,

1000B (08H)

IPBTM, or IP) is set, occurs

<2> When any of P0A0-P0A3 and P0B0-P0B3 pins goes low

Other Than Above

Inhibited

Table 8-2

Operations After HALT Mode Release (1/2)

(a)

HALT 08H

HALT Mode Released by:

Interrupt Status

Interrupt Enable Flag

Operations after HALT Mode Release

Low-Level Input of P0A0-P0A3,

Don’t care

Instruction next to HALT is executed

P0B0-P0B3

Disabled

Standby mode is not released

When Release Condition Is

Enabled

Instruction next to HALT is executed

Satisfied by Interrupt

Disabled

Standby mode is not released

Enabled

Branches to interrupt vector address

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