P89CV51RB2_09 datasheet(13/76 Pages) NXP

13 / 76 page

P89CV51RB2_RC2_RD2_3

Product data sheet

Rev. 03 — 25 August 2009

13 of 76

NXP Semiconductors

P89CV51RB2/RC2/RD2

80C51 with 1 kB RAM, SPI

6.2 Memory organization

The various P89CV51RB2/RC2/RD2 memory spaces are as follows:

• 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.

6.2.1 Expanded data RAM addressing

The P89CV51RB2/RC2/RD2 have 1 kB of data RAM; see Figure 4.

To access the expanded RAM (XRAM), the EXTRAM bit must be set and MOVX

instructions must be used. The expanded memory is physically located on the chip and

logically occupies the ﬁrst bytes of external memory (addresses 000H to 2FFH).

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

Table 5.

AUXR - Auxiliary function register (address 8EH) bit allocation

Not bit addressable; reset value 00H.

Bit

Symbol

EXTRAM

P89CV51RB2 Datasheet(PDF) 13 Page - NXP Semiconductors

P89CV51RB2 Datasheet(HTML) 13 Page - NXP Semiconductors

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76

Datasheet Download

Link URL