W925EP01 Datasheet, PDF (12/108 Pages) Winbond – 8-BIT CID MICROCONTROLLER

W925EP01/ W925EP01FG
Data Memory:
The W925EP01 contains on-chip 4K MOVX RAM of Data Memory, which can only be accessed by
MOVX instructions from the address 000H to FFFH. Access to the on-chip MOVX SRAM is optional
by software setting DME0 to “1”, MOVX addresses greater than FFFH automatically go to external
memory through A0 to A15; this is the default condition. When DME0 be clearing to “0”, the 4K data
memory area is transparent to the system memory map. Any MOVX directed to the space between
0000H to FFFFH goes to expanded bus on A0 to A15.
In addition, the W925EP01 has 256 bytes of on-chip scratchpad RAM. This can be accessed either by
direct addressing or by indirect addressing. There are also 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, the only one selection is external data memory.
However, the on-chip RAM has the fastest access times. The memory map is shown Figure 6-2 and
Figure 6-3 shows the scratched-pad RAM/register addressing.
FFFFH
FFH
80H
7FH
00H
Indirect
Addressing
RAM
Direct &
Indirect
Addressing
RAM
SFRs Direct
Addressing
only
64K bytes External
Data Memory
FFFH
4K byte On-chip SRAM
0000H
0000H
Figure 6-2 Data Memory Map
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