W79E225A_08 Datasheet, PDF (14/203 Pages) Winbond – 8-bit Microcontroller

Preliminary W79E225A/226A/227A Data Sheet
Figure 6-1: W79E22X SERIESA Memory Map
6.3 Auxiliary SRAM
W79E22X SERIES has a 1/2/2 KB of data space SRAM which is read/write accessible and is memory
mapped. This on-chip SRAM is accessed by the MOVX instruction. There is no conflict or overlap
among the 256 bytes scratch-pad memory and the 1/2/2 KB auxiliary sram as they use different
addressing modes and instructions. Access to the on-chip Data Memory is optional under software
control. Set DMEO bit of PMR SFR to 1 will enable the on-chip 1/2/2 KB MOVX SRAM and at the
same time EnNVM bit must be cleared as NVM Data uses the same instruction of MOVX. Refer to.
6.4 NVM Data Flash
W79E22X SERIES 1/2/2-KB NVM Data block shown in the diagram on Figure 6-1 shares the same
address as AUX-RAM address.
Due to overlapping of AUX-RAM, NVM data memory and external data memory physical address, the
following table is defined. EnNVM bit (NVMCON.5) will enable read access to NVM data flash area.
DME0 (PMR.0) will enable read access to AUX-RAM.
ENNVM
0
0
1
DME0
DATA MEMORY AREA
0
Enable External RAM read/write access by MOVX
1
Enable AUX-RAM read/write access by MOVX
Enable NVM data Memory read access by MOVX only. If EER or
X
EWR is set and NVM flash erase or write control is busy, to set
this bit read NVM data is invalid.
Table 6-1: Bits setting for MOVX access to Data Memory Area
INSTRUCTIONS
ENNVM = 1
NVM SIZE = SRAM (1K)
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Publication Release Date: April 15, 2008
Revision A4.0