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W77I058A25PL Datasheet(PDF) 8 Page - Winbond |
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W77I058A25PL Datasheet(HTML) 8 Page - Winbond |
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8 / 82 page  W77IE58/W77I058A - 8 - 6. MEMORY ORGANIZATION The W77I058 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 W77I058 can be up to 64 Kbytes long. There is also on-chip ROM which can be used similarly to that of the 8052, except that the ROM size is 32 Kbytes. All instructions are fetched for execution from this memory area. The MOVC instruction can also access this memory region. Exceeding the maximum address of on-chip ROM will access the external memory. Data Memory The W77I058 can access up to 64Kbytes of external Data Memory. This memory region is accessed by the MOVX instructions. Unlike the 8051 derivatives, the W77I058 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 W77I058 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. 0000h FFFFh 80h 7Fh 00h 64 K Bytes External Data Memory Indirect Addressing RAM Direct & Indirect Addressing RAM SFRs Direct Addressing FFh FFFFh 0000h External Program Memory 7FFFh 32K Bytes On-chip Program Memory 1K Bytes On-chip SRAM 0000h 03FFh Figure 1. Memory Map |
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