am79c940 Advanced Micro Devices, am79c940 Datasheet - Page 56

• Manufacturer Part Number: am79c940
• Description: Media Access Controller For Ethernet Mace
• Manufacturer: Advanced Micro Devices

data without addition of an FCS field, and the FCS will be
calculated and verified at the receiver.
The loopback facilities of the MACE device allow full op-
eration to be verified without disturbance to the network.
Loopback operation is also affected by the state of the
Loopback Control bits (LOOP [0–1]) in the User Test
Register. This affects whether the internal MENDEC is
considered part of the internal or external loop-
back path.
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Am79C940
When in the loopback mode(s), the multicast address
detection feature of the MACE device, programmed by
the contents of the Logical Address Filter (LADR [63–0])
can only be tested when RCVFCSE = 1, allocating the
CRC generator to the receiver. All other features
operate identically in loopback as in normal operation,
such as automatic transmit padding and receive
pad stripping.