P89V51RD2 Philips Semiconductors, P89V51RD2 Datasheet - Page 16

• Manufacturer Part Number: P89V51RD2
• Description: 8-bit 80C51 5 V low power 64 kB Flash microcontroller with 1 kB RAM
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 12964
Product data
When EXTRAM =
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.
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 7:
[1]
AUXR
EXTRAM = 0
EXTRAM = 1
Access limited to ERAM address within 0 to 0FFH; cannot access 100H to 02FFH.
External data memory RD, WR with EXTRAM bit
MOVX @DPTR, A or MOVX A,
@DPTR
ADDR < 0300H
RD/WR not
asserted
RD/WR asserted RD/WR asserted RD/WR asserted
Rev. 01 — 01 March 2004
1
, MOVX @Ri and MOVX @DPTR will be similar to the standard
ADDR
RD/WR asserted RD/WR not asserted
0300H
8-bit microcontrollers with 80C51 core
MOVX @Ri, A or MOVX A, @Ri
ADDR = any
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
P89V51RD2
Table 7
shows external
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