xxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxx x x x xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxx xx xx

xxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxx xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxx x x

xxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxx

xxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxx xxx

[1]

All ports are in input only (high impedance) state after power-up.

[2]

BRGR1 and BRGR0 must only be written if BRGEN in BRGCON SFR is ‘0’. If any are written while BRGEN = 1, the result is unpredictable.

Unimplemented bits in SFRs (labeled ’-’) are X (unknown) at all times. Unless otherwise specified, ones should not be written to these bits since they may be used for other

purposes in future derivatives. The reset values shown for these bits are ‘0’s although they are unknown when read.

[3]

The RSTSRC register reflects the cause of the P89LPC901/902/903 reset. Upon a power-up reset, all reset source flags are cleared except POF and BOF; the power-on reset

value is xx110000.

[4]

After reset, the value is 111001x1, i.e., PRE2-PRE0 are all ‘1’, WDRUN = 1 and WDCLK = 1. WDTOF bit is ‘1’ after Watchdog reset and is ‘0’ after power-on reset. Other resets will

not affect WDTOF.

[5]

On power-on reset, the TRIM SFR is initialized with a factory preprogrammed value. Other resets will not cause initialization of the TRIM register.

[6]

The only reset source that affects these SFRs is power-on reset.

RTCL

Real-time clock register LOW

D3H

00[6]

00000000

SADDR

Serial port address register

A9H

00

00000000

SADEN

Serial port address enable

B9H

00

00000000

SBUF

Serial port data buffer register

99H

xx

xxxxxxxx

Bit address

9F

9E

9D

9C

9B

9A

99

98

SCON*

Serial port control

98H

SM0/FE

SM1

SM2

REN

TB8

RB8

TI

RI

00

00000000

SSTAT

Serial port extended status

register

BAH

DBMOD

INTLO

CIDIS

DBISEL

FE

BR

OE

STINT

00

00000000

SP

Stack pointer

81H

07

00000111

Bit address

8F

8E

8D

8C

8B

8A

89

88

TCON*

Timer 0 and 1 control

88H

TF1

TR1

TF0

TR0

----

00

00000000

TH0

Timer 0 HIGH

8CH

00

00000000

TH1

Timer 1 HIGH

8DH

00

00000000

TL0

Timer 0 LOW

8AH

00

00000000

TL1

Timer 1 LOW

8BH

00

00000000

TMOD

Timer 0 and 1 mode

89H

-

-

T1M1

T1M0

-

-

T0M1

T0M0

00

00000000

TRIM

Internal oscillator trim register

96H

-

-

TRIM.5

TRIM.4

TRIM.3

TRIM.2

TRIM.1

TRIM.0

[5] [6]

WDCON

Watchdog control register

A7H

PRE2

PRE1

PRE0

-

-

WDRUN

WDTOF

WDCLK

[4] [6]

WDL

Watchdog load

C1H

FF

11111111

WFEED1

Watchdog feed 1

C2H

WFEED2

Watchdog feed 2

C3H

Table 9:

* indicates SFRs that are bit addressable.

Name

Description

SFR

addr.

Bit functions and addresses

Reset value

MSB

LSB

Hex

Binary