AM79C987 datasheet(18/30 Pages) AMD

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AMD

P R E L I M I N A R Y

Am79C987

Frames Too Long

P[4:0] = 16–23, 31, R[4:0] = 4

Byte 0

Byte 1

Byte 2

Byte 3

bit 7

bit 31

bit 0

bit 24

MSB

LSB

D Port Read

“Frames Too Long” is a read-only attribute that counts

the number of frames that exceed the maximum valid

packet length of 1518 bytes. This attribute is a 32-bit

counter with a minimum rollover time of 61 days.

Short Events

P[4:0] = 16–23, 31, R[4:0] = 5

Byte 0

Byte 1

Byte 2

Byte 3

bit 7

bit 31

bit 0

bit 24

MSB

LSB

D Port Read

“Short Events” is a read-only attribute that counts the

number of instances where activity is detected with a du-

ration less than the “ShortEventMaxTime” (74–82-bit

times). This attribute is a 32-bit counter with a minimum

rollover time of 16 hours.

Runts

P[4:0] = 16–23, 31, R[4:0] = 6

Byte 0

Byte 1

Byte 2

Byte 3

bit 7

bit 31

bit 0

bit 24

MSB

LSB

D Port Read

“Runts” is a read-only attribute that counts the number of

instances where activity is detected with a duration

greater than the “ShortEventMaxTime” (74–82-bit

times), but less than the minimum valid frame time

(512-bit times, or 64 bytes). This attribute is a 32-bit

counter with a minimum rollover time of 16 hours.

Note: Runts usually indicate collision fragments, a nor-

mal network event. In certain situation associated with

large diameter networks a percentage of runts may ex-

ceed ValidPacketMinTime.

Collisions

P[4:0] = 16–23, 31, R[4:0] = 7

Byte 0

Byte 1

Byte 2

Byte 3

bit 7

bit 31

bit 0

bit 24

MSB

LSB

D Port Read

“Collisions” is a read-only attribute that counts the num-

ber of instances where a carrier is detected on the port,

and a collision is detected. This attribute is a 32-bit

counter with a minimum rollover time of 16 hours.

Late Events

P[4:0] = 16–23, 31, R[4:0] = 8

Byte 0

Byte 1

Byte 2

Byte 3

bit 7

bit 31

bit 0

bit 24

MSB

LSB

D Port Read

“Late Events” is a read-only attribute that counts the

number of instances where a collision is detected after

the LateEventThreshold (480–565-bit times) in the

frame. This event will be counted both by the “Late

Events” attribute, as well as the “Collisions” attribute.

This attribute is a 32-bit counter with a minimum rollover

time of 81 hours.

Very Long Events

P[4:0] = 16–23, 31, R[4:0] = 9

Byte 0

Byte 1

Byte 2

Byte 3

bit 7

bit 31

bit 0

bit 24

MSB

LSB

D Port Read

“Very Long Events” is a read-only attribute that counts

the number of times the transmitter is active in excess of

the MAU Jabber Lockup Protection (MJLP) Timer (4 ms

– 7.5 ms). This attribute is a 32-bit counter with a mini-

mum rollover time of 198 days.

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