W79E225A Datasheet, PDF (14/200 Pages) Winbond – 8-bit Microcontroller

Preliminary W79E225A/227A Data Sheet
Figure 6-1: W79E225/227A Memory Map
6.3 Auxiliary SRAM
W79E225/227 has a 1/2 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 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 KB MOVX SRAM and at the same
time EnNVM bit must be cleared as NVM memory uses the same instruction of MOVX. Refer to.
6.4 NVM Data Flash Memory
W79E225/227 1/2-KB NVM memory block shown in the diagram on
Figure 6-1: shares the same address as AUX-RAM address.
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Publication Release Date: December 14, 2007
Revision A2.0