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数据搜索系统，热门电子元器件搜索 |
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AM79C978VC/W 数据表(PDF) 97 Page - Advanced Micro Devices |
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AM79C978VC/W 数据表(HTML) 97 Page - Advanced Micro Devices |
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97 / 261 page  Am79C978 97 Double Word I/O Mode The Am79C978 controller can be configured to operate in DWord (32-bit) I/O mode. The software can invoke the DWIO mode by performing a DWord write access to the I/O location at offset 10h (RDP). The data of the write access must be such that it does not affect the in- tended operation of the Am79C978 controller. Setting the device into 32-bit I/O mode is usually the first oper- ation after H_RESET or S_RESET. The RAP register will point to CSR0 at that time. Writing a value of 0 to CSR0 is a safe operation. DWIO (BCR18, bit 7) will be set to 1 as an indication that the Am79C978 controller operates in 32-bit I/O mode. Note: Even though the I/O resource mapping changes when the I/O mode setting changes, the RDP location offset is the same for both modes. Once the DWIO bit has been set to 1, only H_RESET can clear it to 0. The DWIO mode setting is unaffected by S_RESET or set- ting of the STOP bit. Table 27 shows how the 32 bytes of address space are used in DWord I/O mode. All I/O resources must be accessed in DWord quanti- ties and on DWord addresses. A read access other than listed in Table 27 will yield undefined data, a write operation may cause unexpected reprogramming of the Am79C978 control registers. Table 25. I/O Map in Word I/O Mode (DWIO = 0) Offset No. of Bytes Register 00h - 0Fh 16 APROM 10h 2 RDP 12h 2 RAP (shared by RDP and BDP) 14h 2 Reset Register 16h 2 BDP 18h - 1Fh 8 Reserved Table 26. Legal I/O Accesses in Word I/O Mode (DWIO = 0) AD[4:0] BE[3:0] Type Comment 0XX00 1110 RD Byte read of APROM location 0h, 4h, 8h, or Ch 0XX01 1101 RD Byte read of APROM location 1h, 5h, 9h, or Dh 0XX10 1011 RD Byte read of APROM location 2h, 6h, Ah, or Eh 0XX11 0111 RD Byte read of APROM location 3h, 7h, Bh, or Fh 0XX00 1100 RD Word read of APROM locations 1h (MSB) and 0h (LSB), 5h and 4h, 8h and 9h, or Ch and Dh 0XX10 0011 RD Word read of APROM locations 3h (MSB) and 2h (LSB), 7h and 6h, Bh and Ah, or Fh and Eh 10000 1100 RD Word read of RDP 10010 0011 RD Word read of RAP 10100 1100 RD Word read of Reset Register 10110 0011 RD Word read of BDP 0XX00 1100 WR Word write to APROM locations 1h (MSB) and 0h (LSB), 5h and 4h, 8h and 9h, or Ch and Dh 0XX10 0011 WR Word write to APROM locations 3h (MSB) and 2h (LSB), 7h and 6h, Bh and Ah, or Fh and Eh 10000 1100 WR Word write to RDP 10010 0011 WR Word write to RAP 10100 1100 WR Word write to Reset Register 10110 0011 WR Word write to BDP 10000 0000 WR DWord write to RDP, switches device to DWord I/O mode |
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