p89cv51rb2 NXP Semiconductors, p89cv51rb2 Datasheet - Page 12

• 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
6.2.1 Expanded data RAM addressing
6.2 Memory organization
The various P89CV51RB2/RC2/RD2 memory spaces are as follows:
The P89CV51RB2/RC2/RD2 have 1 kB of data RAM; see
To access the expanded RAM (XRAM), the EXTRAM bit must be set and MOVX
instructions must be used. The extra memory is physically located on the chip and
logically occupies the first bytes of external memory (addresses 000H to 2FFH).
Table 5.
Not bit addressable; reset value 00H.
When EXTRAM = 1, 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 = 1, the expanded RAM can be accessed as in the following example.
Expanded RAM access (indirect addressing only):
Bit
Symbol
•
•
•
•
•
MOVX @DPTR, A; DPTR contains 0A0H
DATA
128 B of internal data memory space (00H:7FH) accessed via direct or indirect
addressing, using instructions other than MOVX and MOVC. All or part of the stack
may be in this area.
IDATA
Indirect Data. 256 B of internal data memory space (00H:FFH) accessed via indirect
addressing using instructions other than MOVX and MOVC. All or part of the stack
may be in this area. This area includes the DATA area and the 128 B immediately
above it.
SFR
Special Function Registers. Selected CPU registers and peripheral control and status
registers, accessible only via direct addressing.
XDATA
‘External’ Data or auxiliary RAM. Duplicates the classic 80C51 64 kB memory space
addressed via the MOVX instruction using the DPTR, R0, or R1. The
P89CV51RB2/RC2/RD2 have 768 B of on-chip XDATA memory.
CODE
64 kB of code memory space, accessed as part of program execution and via the
MOVC instruction. The P89CV51RB2/RC2/RD2 have 16/32/64 kB of on-chip code
memory.
AUXR - Auxiliary function register (address 8EH) bit allocation
7
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Rev. 01 — 5 October 2007
6
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5
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P89CV51RB2/RC2/RD2
4
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3
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Figure
80C51 with 1 kB RAM, SPI
2
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4.
EXTRAM
© NXP B.V. 2007. All rights reserved.
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