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PSD913F2 数据表(PDF) 29 Page - STMicroelectronics |
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PSD913F2 数据表(HTML) 29 Page - STMicroelectronics |
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29 / 91 page ![]() PSD9XX Family PSD935G2 28 The PSD935G2 Functional Blocks (cont.) Level 1 SRAM, I /O Level 2 Secondary Flash Memory Highest Priority Lowest Priority Level 3 Main Flash Memory Figure 6. Priority Level of Memory and I/O Components 9.1.3.1. Memory Select Configuration for MCUs with Separate Program and Data Spaces The 80C51 and compatible family of microcontrollers, can be configured to have separate address spaces for code memory (selected using PSEN) and data memory (selected using RD). Any of the memories within the PSD935G2 can reside in either space or both spaces. This is controlled through manipulation of the VM register that resides in the PSD’s CSIOP space. The VM register is set using PSDsoft to have an initial value. It can subsequently be changed by the microcontroller so that memory mapping can be changed on-the-fly. For example, you may wish to have SRAM and main Flash in Data Space at boot, and secondary Flash memory in Program Space at boot, and later swap main and secondary Flash memory. This is easily done with the VM register by using PSDsoft to configure it for boot up and having the microcontroller change it when desired. Table 11 describes the VM Register. Bit 7 Bit 6* Bit 5* Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 PIO_EN FL_Data Boot_Data FL_Code Boot_Code SRAM_Code 0 = disable ** 0 = RD 0 = RD 0 = PSEN 0 = PSEN 0 = PSEN PIO mode can’t can’t can’t can’t can’t access access access access access Flash Boot Flash Flash Boot Flash SRAM 1= enable ** 1 = RD 1 = RD 1 = PSEN 1 = PSEN 1 = PSEN PIO mode access access access access access Flash Boot Flash Flash Boot Flash SRAM Table 11. VM Register NOTE: Bits 6-5 are not used. |
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