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DP83905AVQB Datasheet(PDF) 28 Page - National Semiconductor (TI) |
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DP83905AVQB Datasheet(HTML) 28 Page - National Semiconductor (TI) |
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28 / 80 page  50 Register Descriptions (Continued) 52 SHARED MEMORY MODE CONTROL REGISTERS The following tables describe the functionality of the two control registers and the 816 detection registers Shared Memory AT Detect Register (Read only) 76543210 xxxxxxx ATDET Bits Symbols Function D0 ATDET ATDET This bit shows the value on the DWID pin and can be read by software to determine whether the ATLANTIC Controller is operating in an 8- or 16-bit slot When this bit is read as a 1 the ATLANTIC Controller is in a 16-bit slot (PC-AT system bus) and when read asa0itisinan 8-bit slot Shared Memory Control Register 1 76543210 RESET MEME A18 A17 A16 A15 A14 A13 Bits Symbols Function D0-D5 A13–A18 A13 – 18 Lower part of the address register used to determine the position of the ATLANTIC Controller’s memory within the system memory map D6 MEME MEMORY ENABLE Enables external memory accesses when held high This bit will power up low so the user must program the base memory address and set this bit high to enable the memory into the system’s memory map D7 RESET RESET Resets NIC core of ATLANTIC Controller Shared Memory Control Register 2 76 5 4 3210 816 MEMW Unused LA23 LA22 LA21 LA20 LA19 Bits Symbols Function D0–D4 LA19–LA23 LA19 – 23 Upper part of the address register used to determine the position of the ATLANTIC Controller’s memory within the system memory map D5 UNUSED D6 MEMW MEMORY WIDTH Sets width of external memory When set low external memory is accessed as byte wide so only 8 kbytes of memory are available When set high external memory is accessed as word wide so 16 kbytes are available In non-compatible mode up to 64 kbytes of external memory is allowed when this bit is set high or 32 kbytes when low When bit 7 is set high this bit must also be set high D7 816 816-BIT Allows 16-bit system accesses to external memory when set high When low only 8-bit accesses are allowed When high the generation of the M16 output is allowed 28 |
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