W77IE58 Datasheet, PDF (11/90 Pages) Winbond – 8-BIT MICROCONTROLLER

Preliminary W77IE58
Data Memory
The W77IE58 can access up to 64Kbytes of external Data Memory. This memory region is accessed by
the MOVX instructions. Unlike the 8051 derivatives, the W77IE58 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 Port 0 and 2. This is the default
condition. In addition, the W77IE58 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
FFFFh
64 K
Bytes
External
Data
Memory
03FFh
0000h
1K Bytes
On-chip SRAM
0000h
FFFFh
External
Program
Memory
7FFFh
0000h
32K Bytes
On-chip
Program
Memory
Figure 1. Memory Map
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Publication Release Date: July 2000
Revision A1