am79c940 Advanced Micro Devices, am79c940 Datasheet - Page 73

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

Loop [1–0]
00
01
10
11
Loopback Functions
No Loopback
External Loopback
Internal Loopback, excludes
MENDEC
Internal Loopback, includes
MENDEC
External loopback allow the
MACE device to transmit to the
physical medium, using either
the AUI, 10BASE-T, DAI or GPSI
port,
PORTSEL [1–0] bits in the PLS
dependent
Function
on
the
Am79C940
Bit 0
Reserved Test Register 1 (RTR1)
Reserved for AMD internal use only.
Reserved Test Register 2 (RTR2)
Reserved for AMD internal use only.
RES
Configuration Control register.
Using the internal loopback test
will ensure that transmission
does not disturb the physical me-
dium and will prohibit frame re-
ception from the network. One
Internal loopback function in-
cludes the MENDEC in the loop.
Reserved. Read as zero. Always
write as zero.
(REG ADDR 30)
(REG ADDR 31)
AMD
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