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PC87570-ICC/VUL 数据表(PDF) 31 Page - National Semiconductor (TI) |
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PC87570-ICC/VUL 数据表(HTML) 31 Page - National Semiconductor (TI) |
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31 / 168 page  Signal/Pin Connection and Description 31 www.national.com 2.8.1 Accessing Base Memory Base Memory Configuration The environment setting controls the use of on-chip Base Memory (ROM), or off-chip Base Memory. In all cases, the memory access parameters (i.e., the number of wait and hold cycles) are as defined for zone1 of the BIU. On-Chip Base Memory In IRE environment, on-chip ROM is used as Base Memory, as shown in Figure 2-2. To maximize on-chip ROM perfor- mance, configure the BIU as described in Section 3.6 on page 46. Off-Chip Base Memory In IRD and Dev environments (when on-chip ROM is not available), the code and constant data are stored in off-chip Base Memory. This off-chip Base Memory has 64 Kbytes of address space (10000h - 1FFFFh). The first 56 Kbyte are also shadowed to address (00000h - 0DFFFh), when MCFG.SHOFF=0. Off-chip accesses to this memory zone are indicated by the SEL1 output. Figure 2-3 illustrates how off-chip Base Memory is mapped to the PC87570’s address space. Table 2-6. PC87570 Memory Map 1. See Section 2.8.1 for details. 2. See Section 2.8.2 for details. 3. When MCFG.A15E = 1; otherwise reserved. 4. See Appendix A on page 156 for details of the implemented registers. PC87570 CS A0-18 D0-7 ROMOE MEMWR ROMCS SHBM A0-18 SEL0 D0-7 A0-18 D0-7 HA0-18 IORD IOWR HD0-7 IORD IOWR MEMRD MEMWR MEMCS HAEN AEN HIOCHRDY IOCHRDY Figure 2-1. Sharing PC87570 Program Memory and BIOS Flash Memory RD RD WR WR0 BIOS Flash Memory Address Size (Bytes) Description Environment Shadow On1 Shadow Off 2 00000h − 007FFh 2K Base Memory External Memory IRE 00800h − 07FFFh 30K Reserved 08000h − 0DFFFh 24K External Memory 3 00000h − 0DFFFh 56K Base Memory External Memory IRD, Dev 0E000h - 0EFFFh 4K Reserved All 0F000h − 0F3FFh 1K System RAM 0F400h - 0F8FFh 1280 Reserved 0F900h - 0F90Ah 11 HBI 0F90Bh - oF97Fh 117 Reserved 0F980h − 0F98Fh 16 BIU Registers4 0F990h - 0FAFFh 368 Reserved 0FB00h − 0FBFFh 256 I/O Expansion 0FC00h − 0FFFFh 1K On-chip modules registers4 10000h − 107FFh 2K Base Memory IRE 10800h − 1FFFFh 62K Reserved 10000h − 1FFFFh 64K Base Memory IRD, Dev 20000h − 3FFFFh 128K Reserved All |
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