P89LPC9321 datasheet(45/70 Pages) NXP

45 / 70 page

P89LPC9321_1

Product data sheet

Rev. 01 — 9 December 2008

45 of 70

NXP Semiconductors

P89LPC9321

8-bit microcontroller with accelerated two-clock 80C51 core

7.29 Additional features

7.29.1 Software reset

The SRST bit in AUXR1 gives software the opportunity to reset the processor completely,

as if an external reset or watchdog reset had occurred. Care should be taken when writing

to AUXR1 to avoid accidental software resets.

7.29.2 Dual data pointers

The dual Data Pointers (DPTR) provides two different Data Pointers to specify the address

used with certain instructions. The DPS bit in the AUXR1 register selects one of the two

Data Pointers. Bit 2 of AUXR1 is permanently wired as a logic 0 so that the DPS bit may

be toggled (thereby switching Data Pointers) simply by incrementing the AUXR1 register,

without the possibility of inadvertently altering other bits in the register.

7.29.3 Data EEPROM

The P89LPC9321 has 512 bytes of on-chip Data EEPROM. The Data EEPROM is SFR

based, byte readable, byte writable, and erasable (via row ﬁll and sector ﬁll). The user can

read, write and ﬁll the memory via SFRs and one interrupt. This Data EEPROM provides

100,000 minimum erase/program cycles for each byte.

• Byte mode: In this mode, data can be read and written one byte at a time.

• Row ﬁll: In this mode, the addressed row (64 bytes) is ﬁlled with a single value. The

entire row can be erased by writing 00H.

• Sector ﬁll: In this mode, all 512 bytes are ﬁlled with a single value. The entire sector

can be erased by writing 00H.

(1) Watchdog reset can also be caused by an invalid feed sequence, or by writing to WDCON not immediately followed by a feed

sequence.

Fig 20. Watchdog timer in Watchdog mode (WDTE = 1)

PRE2

PRE1

PRE0

WDRUN

WDTOF

WDCLK

WDCON (A7H)

SHADOW REGISTER

PRESCALER

002aae015

8-BIT DOWN

COUNTER

WDL (C1H)

watchdog

oscillator

external

crystal

oscillator

PCLK

XTALWD

÷32

MOV WFEED1, #0A5H

MOV WFEED2, #05AH

reset(1)

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