
AMD |
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Am79C930 Device ISA Plug And Play Mode Memory And I/O Resource Requirements |
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Memory Range | Memory Size |
| I/O Range |
| I/O Size |
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MBA*+0000h – | 32 Kbytes |
| IOBA**+0000h – IOBA**+000Fh |
| 16 bytes |
MBA*+7FFFh | OR |
| and I/O 0279h and I/O 0A79h |
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| 0 bytes |
| and I/O 0203h – I/O 03FFh (one byte only) |
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*MBA = ISA Plug and Play Memory Base Address **IOBA = ISA Plug and Play I/O Base Address
Note that since the Am79C930 device's memory mapped resources are all accessible through the Local Memory Address Register and I/O Data Ports (SIR2,3,4,5,6,7), it is possible to program the ISA Plug and Play Memory Base Address, and Memory upper limit Address or range length for descriptor 0, such that the Am79C930 device is assigned no memory space. (This is accomplished by assigning all 0s for both the Memory Base Address and the Memory range length value. The ISA Plug and Play utility can be instructed to make this selection through appropriate Resource Data programming.) By assigning no memory space to the Am79C930 device, the Am79C930 device will become an I/O only device. Such an arrangement may be con- venient for systems in which there is not enough total available memory space to allow the Am79C930 device to use a full 32K block of memory. Note that when this option is chosen, the total amount of bus bandwidth re- quired to perform all of the necessary accesses to the
The Am79C930 device requires the use of a single IRQ channel. Any of the following channels within an ISA Plug and Play system may be utilized by the Am79C930 device:
IRQ 4, 5, 9, 10, 11 or 12.
ISA Plug and Play Memory Resources — While the system memory space of the Am79C930 device only accommodates access to 32 Kbytes of memory, the Am79C930 device uses device select and bank select bits in SIR1 in order to access a total of 256K of memory space. Note that ISA accesses to memory locations
32 Kbytes of memory:
Am79C930 Device ISA Plug And Play Mode Memory Map
ISA Address in Memory | SIR1[5:3] | Size of Space | Physical Memory |
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MBA+0000h – MBA+7FFFh | 000 | 32 Kbytes | SRAM Memory 0 | 0000h | – 0 7FFFh |
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MBA+0000h – MBA+7FFFh | 001 | 32 Kbytes | SRAM Memory 0 | 8000h | – 0 FFFFh |
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MBA+0000h – MBA+7FFFh | 010 | 32 Kbytes | SRAM Memory 1 | 0000h | – 1 7FFFh |
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MBA+0000h – MBA+7FFFh | 011 | 32 Kbytes | SRAM Memory 1 8000h – 1 FFFFh | ||
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MBA+0000h – MBA+7FFFh | 100 | 32 Kbytes | Flash Memory 0 0000h – 0 7FFFh | ||
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MBA+0000h – MBA+7FFFh | 101 | 32 Kbytes | Flash Memory 0 8000h – 0 FFFFh | ||
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MBA+0000h – MBA+7FFFh | 110 | 32 Kbytes | Flash Memory 1 0000h – 1 7FFFh | ||
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MBA+0000h – MBA+7FFFh | 111 | 32 Kbytes | Flash Memory 1 8000h – 1 FFFFh | ||
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| TOTAL: | 256 Kbytes |
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*MBA = ISA Plug and Play Memory Base Address
When accessing Am79C930 memory resources through ISA memory cycle accesses, the upper 9 bits of the ISA memory address will be used to check for a match of the address range assigned to the Am79C930 device by the Plug and Play configuration program (i.e.,
the Memory Base Address = MBA, and Memory range length). The Plug and Play configuration program will have written a memory base address value into the Memory Base Address registers (Plug and Play ports 40h and 41h). The ISA Plug and Play memory base
64 | Am79C930 |