DP83905AVQB National Semiconductor, DP83905AVQB Datasheet - Page 64

• Manufacturer Part Number: DP83905AVQB
• Description: IC CONTROLR AT/LAN TP IN 160PQFP
• Manufacturer: National Semiconductor
• Series: AT/LANTIC™r

Specifications of DP83905AVQB

• Controller Type: AT, LAN Twisted-Pair Interface Controller
• Voltage - Supply: 4.75 V ~ 5.25 V
• Current - Supply: 100mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 160-BFQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Interface: -
• Other names: *DP83905AVQB

6 0 Operation of AT LANTIC Controller
(Continued)
8-Bit Shared Memory Mode Read Bus Timing with DWID High
TL F 11498 – 47
This is the type of cycle used to read 8 bits from buffer RAM in shared memory mode when DWID is high These accesses are
entirely asynchronous with the AT LANTIC Controller responding when it decodes the correct address on LA17– 23 SA0– 19
and a MRD If AEN is high the cycle will be ignored CHRDY is deasserted if the AT LANTIC Controller is not ready to respond
and asserted when ready If it is ready immediately CHRDY is not deasserted The 8 16-bit in Control Register 2 must be set to
allow generation of M16 This will be generated whenever the LA17– 23 lines match the corresponding values in Control
Register 2 It will therefore be generated for a full 128 kbytes of address space although the AT LANTIC Controller will occupy
less than that It may be preferable to only set the 8 16-bit for the duration of a transfer from the buffer RAM The AT LANTIC
Controller will also compare the address line programmed in Control Register 1 before allowing accesses to buffer RAM and
therefore do a complete decode The system indicates that this is an 8-bit transfer by not asserting SBHE for an even address
SA0 low or by accessing an odd address SA0 high If the 8 16-bit is low the AT LANTIC Controller will only drive data onto
SD0 –7 Even addresses will use RCS1 and MSD0–7 odd addresses will use RCS2 and MSD8– 15 If 8 16-bit is high the
AT LANTIC Controller can drive either SD0–7 or SD8–15 Even addresses are fetched using RCS1 and MSD0 – 7 and driven
onto SD0 –7 Odd addresses are fetched using RCS2 and MSD8 – 15 and driven onto SD8 – 15
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