P89V51RB2BA View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

P89V51RB2BA

8-bit 80C51 5 V low power 16/32/64 kB Flash microcontroller with 1 kB RAM

Philips Electronics 

Philips Semiconductors

P89V51RB2/RC2/RD2

8-bit microcontrollers with 80C51 core

When EXTRAM = 0, the expanded RAM is indirectly addressed using the MOVX

instruction in combination with any of the registers R0, R1 of the selected bank or

DPTR. Accessing the expanded RAM does not affect ports P0, P3.6 (WR), P3.7

(RD), or P2. With EXTRAM = 0, the expanded RAM can be accessed as in the

following example.

Expanded RAM Access (Indirect Addressing only):

MOVX@DPTR, A DPTR contains 0A0H

DPTR points to 0A0H and data in ‘A’ is written to address 0A0H of the expanded

RAM rather than external memory. Access to external memory higher than 2FFH

using the MOVX instruction will access external memory (0300H to FFFFH) and will

perform in the same way as the standard 8051, with P0 and P2 as data/address bus,

and P3.6 and P3.7 as write and read timing signals.

When EXTRAM = 1, MOVX @Ri and MOVX @DPTR will be similar to the standard

8051. Using MOVX @Ri provides an 8-bit address with multiplexed data on Port 0.

Other output port pins can be used to output higher order address bits. This provides

external paging capabilities. Using MOVX @DPTR generates a 16-bit address. This

allows external addressing up the 64 kB. Port 2 provides the high-order eight address

bits (DPH), and Port 0 multiplexes the low order eight address bits (DPL) with data.

Both MOVX @Ri and MOVX @DPTR generates the necessary read and write

signals (P3.6 - WR and P3.7 - RD) for external memory use. Table 9 shows external

data memory RD, WR operation with EXTRAM bit.

The stack pointer (SP) can be located anywhere within the 256 bytes of internal RAM

(lower 128 bytes and upper 128 bytes). The stack pointer may not be located in any

part of the expanded RAM.

Table 9: External data memory RD, WR with EXTRAM bit

AUXR

MOVX @DPTR, A or MOVX A,

@DPTR

MOVX @Ri, A or MOVX A, @Ri

ADDR < 0300H ADDR ≥ 0300H ADDR = any

EXTRAM = 0

RD/WR not

asserted

RD/WR asserted RD/WR not asserted

EXTRAM = 1

RD/WR asserted RD/WR asserted RD/WR asserted

[1] Access limited to ERAM address within 0 to 0FFH; cannot access 100H to 02FFH.

9397 750 14341

Product data

Rev. 03 — 02 December 2004

© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

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