W77E532 Datasheet, PDF (8/86 Pages) Winbond – 8 BIT MICROCONTROLLER

W77E532/W77E532A
6. MEMORY ORGANIZATION
The W77E532A separates the memory into two separate sections, the Program Memory and the Data
Memory. The Program Memory is used to store the instruction op-codes, while the Data Memory is
used to store data or for memory mapped devices.
Program Memory
The Program Memory on the standard 8052 can only be addressed to 64 Kbytes long. By invoking the
banking methodology, W77E532A can extend to two 64KB flash EPROM banks, APFLASH0 and
APFLASH1. There are on-chip ROM banks which can be used similarly to that of the 8052. All
instructions are fetched for execution from this memory area. The MOVC instruction can also access
this memory region. There is an auxiliary 4KB Flash EPROM bank (LDFLASH) resided user loader
program for In-System Programming (ISP). Both APFLASHs allow serial or parallel download
according to user loader program in LDFLASH.
Data Memory
The W77E532A can access up to 64Kbytes of external Data Memory. This memory region is accessed
by the MOVX instructions. Unlike the 8051 derivatives, the W77E532A 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 W77E532A 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
Indirect
Addressing
RAM
80h
7Fh
Direct &
Indirect
Addressing
00h
RAM
SFRs
Direct
Addressing
03FFh
0000h
1K Bytes
On-chip SRAM
64 K
Bytes
External
Data
Memory
FFFFh
64K Bytes
On-chip
Program
Memory
APROM0
64K Bytes
On-chip
Program
Memory
APROM1
0000h
Figure 1. Memory Map
4K Bytes
LDROM
0FFFh
Publication Release Date: June 30, 2009
-8-
Revision A10