P89LPC9211FDH datasheet(43/75 Pages) NXP

43 / 75 page

P89LPC92X1

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Product data sheet

Rev. 2 — 1 December 2010

43 of 75

NXP Semiconductors

P89LPC9201/9211/922A1/9241/

8-bit microcontroller with 8-bit ADC

7.27 Additional features

7.27.1 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.

7.27.2 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

7.28 Flash program memory

7.28.1 General description

The P89LPC9201/9211/922A1/9241/9251 flash memory provides in-circuit electrical

erasure and programming. The flash can be erased, read, and written as bytes. The

Sector and Page Erase functions can erase any flash sector (1 kB) or page (64 bytes).

The Chip Erase operation will erase the entire program memory. ICP using standard

commercial programmers is available. In addition, IAP and byte-erase allows code

memory to be used for non-volatile data storage. On-chip erase and write timing

generation contribute to a user-friendly programming interface. The

P89LPC9201/9211/922A1/9241/9251 flash reliably stores memory contents even after

100,000 erase and program cycles. The cell is designed to optimize the erase and

(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 14. 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

crystal

oscillator

PCLK

XTALWD

÷32

MOV WFEED1, #0A5H

MOV WFEED2, #05AH

reset(1)

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