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Data memory – Rainbow Electronics T89C51CC01 User Manual

Page 21

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21

T89C51CC01

Rev. D – 17-Dec-01

7. Data Memory

The T89C51CC01 provides data memory access in two different spaces:

1.

The internal space mapped in three separate segments:

the lower 128 bytes RAM segment.

the upper 128 bytes RAM segment.

the expanded 1024 bytes RAM segment (ERAM).

2.

The external space.

A fourth internal segment is available but dedicated to Special Function Registers,
SFRs, (addresses 80h to

FFh

) accessible by direct addressing mode.

Figure 2 shows the internal and external data memory spaces organization.

Figure 1. Internal memory - RAM

Figure 2. Internal and External Data Memory Organization ERAM-XRAM

Upper

128 bytes

Internal RAM

Lower

128 bytes

Internal RAM

Special

Function

Registers

80h

80h

00h

FFh

FFh

direct addressing

addressing

7Fh

direct or indirect

indirect addressing

256 up to 1024 bytes

00h

64 Kbytes

External XRAM

0000h

FFFFh

Internal ERAM

EXTRAM= 0

EXTRAM= 1

FFh or 3FFh

Internal

External