AM79C970A Просмотр технического описания (PDF) - Advanced Micro Devices

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AM79C970A

PCnet™-PCI II Single-Chip Full-Duplex Ethernet Controller for PCI Local Bus Product

Advanced Micro Devices 

7) Description: The LAPP mode does not function properly on the PCnet-PCI II device. In LAPP mode, the

PCnet-PCI II device might skip buffers when writing a receive frame to memory.

Implication: The LAPP function cannot be used.

Workaround: None.

Status: No current plan to fix this item.

8) Description: When a transmit frame has excessively deferred to receive activity, the EXDEF bit is not set

in the transmit descriptor.

Implication: Software cannot use the EXDEF bit in the transmit descriptor as an indication of excessive defer-

ral.

Workaround: The excessive deferral interrupt (EXDINT; CSR5, bit 7) does function correctly. User can enable

this interrupt by setting the EXDINTE bit in CSR5.

Status: No current plan to fix this item.

9) Description: The PCnet-PCI device will intermittently give BABL error indications when the network traffic

has frames equal to or greater than 1518 bytes.

Implication: False BABL errors on the receiving station can be passed up to the upper layer software if the

PCnet-PCI II device is just coming out of deferral and the multi-purpose counter used to count the number of

bytes received reaches 1518 at the same time. If the network is heavily loaded with full-size frames, then the

probability of a false BABL error is high.

Workaround: There are two possible workarounds.

1. If the user has no intention to transmit frames larger than 1518 bytes, then the BABL bit may be masked

to ignore babble errors. In this case the false babble error will not cause an interrupt, nor will it be

passed to the higher level software.

2. Check to see if the device is transmitting in ISR (Interrupt Service Routine), which is induced by the

BABL error. The BCRs which control the LED settings can be programmed to indicate a transmit activ-

ity, assuming the interrupt latency is not longer than one minimum IFG (inter-frame gap) time.

If (ISR_LATENCY <9.6 us)

True_bable_err=BABL*(TINT + XMT_LED)

{i.e. False_bable_err=~(BABL*(TINT + XMT_LED))}

else

Cannot tell if the BABL error is true or false just by reading BABL, TINT, XMT_LED bits in ISR.

Status: No current plan to fix this item.

Am79C976

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