W77E468 查看數據表（PDF） - Winbond

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W77E468

8 BIT MICROCONTROLLER

Winbond 

Preliminary W77E468

Data Memory:

The W77E468 can access up to 64Kbytes of external Data Memory. This memory region is accessed

by the MOVX instructions. Unlike the 8051 derivatives, the W77E468 contains on-chip 1K bytes

MOVX SRAM of Data Memory, which can only be accessed by MOVX instructions. These 1K bytes of

SRAM are between address 0000H and 03FFH. Access to the on-chip MOVX SRAM is optional under

software control. When enabled by software, any MOVX instruction that uses this area will go to the

on-chip RAM. MOVX addresses greater than 03FFH automatically go to external memory through

Port 0 and 2. When disabled, the 1KB memory area is transparent to the system memory map. Any

MOVX directed to the space between 0000H and FFFFH goes to the expanded bus on A0-A15 and

D0-D7. This is the default condition. In addition, the W77E468 has the standard 256 bytes of on-chip

Scratchpad RAM. This can be accessed either by direct addressing or by indirect addressing. There

are also some Special Function Registers (SFRs), which can only be accessed by direct addressing.

Since the Scratchpad RAM is only 256 bytes, it can be used only when data contents are small. In the

event that larger data contents are present, two selections can be used. One is on-chip MOVX SRAM

, the other is the external Data Memory. The on-chip MOVX SRAM can only be accessed by a MOVX

instruction, the same as that for external Data Memory. However, the on-chip RAM has the fastest

access times.

FFh

80h

7Fh

00h

Indirect

Addressing

RAM

Direct &

Indirect

Addressing

RAM

SFRs

Direct

Addressing

only

FFFFh

64 K

Bytes

External

Data

Memory

03FFh

1K Bytes

0000h On-chip SRAM

0000h

FFFFh

External

Program

Memory

7FFFh

0000h

32K Bytes

On-chip

Program

Memory

Figure 1. Memory Map

Publication Release Date: January 1999

-9-

Revision A1

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