p89cv51rb2 NXP Semiconductors, p89cv51rb2 Datasheet - Page 13

• Manufacturer Part Number: p89cv51rb2
• Description: P89cv51rb2/rc2/rd2 8-bit 80c51 5 V Low Power 64 Kb Flash Microcontroller With 1 Kb Ram, Spi, 6-clock Cpu With 6/12-clock Peripherals
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89CV51RB2_RC2_RD2_1
Product data sheet
The DPTR points to location 0A0H and the data in the accumulator is written to address
0A0H of the expanded RAM rather than off-chip external memory. Access to EXTRAM
addresses that are not present on the device (above 2FFH) will access external off-chip
memory 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.
Table 6.
When EXTRAM = 0, 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 to 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.
with EXTRAM bit.
The stack pointer (SP) can be located anywhere within the 256 B of internal RAM (lower
128 B and upper 128 B). The stack pointer may not be located in any part of the expanded
RAM.
Table 7.
Bit
7 to 2
1
0
AUXR
EXTRAM = 0
EXTRAM = 1
AUXR - Auxiliary function register (address 8EH) bit description
External data memory RD, WR with EXTRAM bit
Symbol
-
EXTRAM
AO
MOVX @DPTR, A or MOVX A, @DPTR
ADDR < 0300H
RD/WR asserted
RD/WR not asserted
Rev. 01 — 5 October 2007
Description
Reserved for future use. Should be set to 0 by user programs.
Internal/external RAM access using MOVX @Ri/@DPTR. When 1,
accesses internal XRAM with address specified in MOVX instruction.
If address supplied with this instruction exceeds on-chip available
XRAM, off-chip RAM is accessed. When 0, every MOVX instruction
targets external data memory by default.
ALE off: disables/enables ALE. AO = 0 results in ALE emitted at a
constant rate of
active only during a MOVX or MOVC.
Table 7
ADDR
RD/WR asserted
RD/WR asserted
shows external data memory RD, WR operation
1
P89CV51RB2/RC2/RD2
2
the oscillator frequency. In case of AO = 1, ALE is
0300H
MOVX @Ri, A or MOVX A, @Ri
ADDR = any
RD/WR asserted
RD/WR not asserted
80C51 with 1 kB RAM, SPI
© NXP B.V. 2007. All rights reserved.
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