P87LPC778 datasheet(65/79 Pages) PHILIPS

65 / 79 page

Philips Semiconductors

P87LPC778

CMOS single-chip 8-bit microcontroller

Product data

Rev. 01 — 31 March 2004

65 of 79

9397 750 12378

8.17 Additional features

The AUXR1 register contains several special purpose control bits that relate to

several chip features. AUXR1 is described in Tables 58 and 59.

Table 57:

Watchdog rate select clock time

WDS[2:0]

Timeout clocks

Minimum time

Nominal time

Maximum time

0 0 0

8,192

10 ms

16 ms

23 ms

0 0 1

16,384

20 ms

32 ms

45 ms

0 1 0

32,768

41 ms

65 ms

90 ms

0 1 1

65,536

82 ms

131 ms

180 ms

1 0 0

131,072

165 ms

262 ms

360 ms

1 0 1

262,144

330 ms

524 ms

719 ms

1 1 0

524,288

660 ms

1.05 sec

1.44 sec

1 1 1

1,048,576

1.3 sec

2.1 sec

2.9 sec

Table 58:

AUXR1 - AUXR1 register (address A2H) bit allocation

Not bit addressable; Reset value: 00H

Bit

Symbol

KBF

BOD

BOI

LPEP

SRST

DPS

Table 59:

AUXR1 - AUXR1 register (address A2H) bit description

Bit

Symbol

Description

KBF

Keyboard Interrupt Flag. Set when any pin of port 0 that is enabled

for the Keyboard Interrupt function goes LOW. Must be cleared by

software.

BOD

Brown Out Disable. When set, turns off brownout detection and

saves power. See Section 8.11 “Power monitoring functions” on

page 42 for details.

BOI

Brown Out Interrupt. When set, prevents brownout detection from

causing a chip reset and allows the brownout detect function to be

used as an interrupt. See Section 8.11 “Power monitoring

functions” on page 42 for details.

LPEP

Low Power EPROM control bit. Allows power savings in low

voltage systems. Set by software. Can only be cleared by

Power-on or brownout reset. See Section 8.12 “Power reduction

modes” on page 43 for details.

SRST

Software Reset. When set by software, resets the P87LPC778 as

if a hardware reset occurred.

This bit contains a hard-wired 0. Allows toggling of the DPS bit by

incrementing AUXR1, without interfering with other bits in the

Reserved for future use. Should not be set to ‘1’ by user programs.

DPS

Data Pointer Select. Chooses one of two Data Pointers for use by

the program. See text for details.

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