P87LPC779 datasheet(39/74 Pages) PHILIPS

39 / 74 page

Philips Semiconductors

P87LPC779

CMOS single-chip 8-bit microcontroller

Product data

Rev. 02 — 03 May 2004

39 of 74

9397 750 13213

Some chip functions continue to operate and draw power during Power-down mode,

increasing the total power used during Power-down. These include the Brownout

Detect, Watchdog Timer, and Comparators.

8.12.3

Low voltage EPROM operation

The EPROM array contains some analog circuits that are not required when VDD is

less than 4 V, but are required for a VDD greater than 4 V. The LPEP bit (AUXR.4),

when set by software, will Power-down these analog circuits resulting in a reduced

supply current. LPEP is cleared only by power-on reset, so it may be set ONLY for

applications that always operate with VDD less than 4 V.

Table 28:

Interrupt sources

Wake-up Source

Conditions

External Interrupt 0 or 1

The corresponding interrupt must be enabled.

Keyboard Interrupt

The keyboard interrupt feature must be enabled and properly

set up. The corresponding interrupt must be enabled.

Comparator 1 or 2

The comparator(s) must be enabled and properly set up. The

corresponding interrupt must be enabled.

Watchdog Timer Reset

The Watchdog timer must be enabled via the WDTE bit in the

UCFG1 EPROM conﬁguration byte.

Watchdog Timer Interrupt

The WDTE bit in the UCFG1 EPROM conﬁguration byte must

not be set. The corresponding interrupt must be enabled.

Brownout Detect Reset

The BOD bit in AUXR1 must not be set (brownout detect not

disabled). The BOI bit in AUXR1 must not be set (brownout

interrupt disabled).

Brownout Detect Interrupt

The BOD bit in AUXR1 must not be set (brownout detect not

disabled). The BOI bit in AUXR1 must be set (brownout interrupt

enabled). The corresponding interrupt must be enabled.

Reset Input

The external reset input must be enabled.

A/D Converter

Must use internal RC clock (RCCLK = 1) for A/D converter to

work in Power-down mode. The A/D must be enabled and

properly set up. The corresponding interrupt must be enabled.

Table 29:

PCON - Power control register (address 87H) bit allocation

Not bit addressable; Reset value: 30H for a Power-on reset; 20H for a Brownout reset; 00H for

other reset sources.

Bit

Symbol

SMOD1

SMOD0

BOF

POF

GF1

GF0

IDL

Table 30:

PCON - Power control register (address 87H) bit description

Bit

Symbol

Description

SMOD1

When set, this bit doubles the UART baud rate for modes 1, 2, and

SMOD0

This bit selects the function of bit 7 of the SCON SFR. When 0,

SCON.7 is the SM0 bit. When 1, SCON.7 is the FE (Framing Error)

ﬂag. See Tables 36 and 37 for additional information.

BOF

Brown Out Flag. Set automatically when a brownout reset or

interrupt has occurred. Also set at Power-on. Cleared by software.

Refer to Section 8.11 “Power monitoring functions” on page 37 for

additional information.

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