AM79C983A Advanced Micro Devices, AM79C983A Datasheet - Page 27

• Manufacturer Part Number: AM79C983A
• Description: Integrated Multiport Repeater 2 (IMR2)
• Manufacturer: Advanced Micro Devices

In the QuIET device mode, DIR[1] has the following values:
DIR[1]
DIR[1] continually cycles. The state of DIR changes
once every 50-bit times (1-bit time = 100 ns). When
DIR[1] switches from 1 to 0, the QuIET device re-
sponds in the following format:
01010A
S
Each character corresponds to a bit. Each bit is held for 2-
bit times (200 ns). The IMR2 device uses the 01010 pre-
amble to determine if the transceiver is a QuIET device. If
any other sequence is received, the SDATA[n] pins be-
have as if a non-QuIET device transceiver is connected.
On the SDATA[n] pins that return the correct preamble,
the IMR2 device transmits the following sequence
when DIR[1] switches from 0 to 1.
0E
01010
A
B
C
D
S
E
F
G
H
S
2
0
0
0
n
0
n
0
0
0
0
S
0
F
A
B
E
C
D
H
E
G
3
1
1
1
1
1
1
1
1
1
F
A
B
E
E
C
D
H
G
2
2
2
2
2
2
2
2
F
2
0
E
A
B
E
C
D
H
G
A
3
3
3
3
3
3
3
3
F
1
3
A
0
0
1
F
Extended Distance
0
1
Link Test
0
1
Link Pulse Transmit
0
1
Reverse Received Polarity
0
1
Spares - Will be logic HIGH.
2
1
A
F
3
2
Preamble
Device ID (0000 for QuIET)
0
1
0
1
0
1
Spares - Will be logic HIGH.
B
F
3
0
QuIET device drives SDATA with sta-
tus and device ID.
IMR2 device drives QuIET device
with commands.
G
B
Disabled
Disabled
0
Disabled
Enabled
Disabled
Enabled
Enabled
Enabled
1
G
B
Link Fail
Link Pass
Received polarity is reversed.
Received polarity is correct.
No Jabber
Jabber
1
2
G
B
2
3
G
C
3
0
H
C
0
H
1
C
1
H
2
C
2
H
3
3
D
S
0
0
D
S
1
1
S
P R E L I M I N A R Y
D
2
2
S
D
3
S
3
S
4
S
0
Am79C983A
S
5
S
1
6
Control and Status for Non-QuIET Transceivers
On the SDATA[n] pins that do not return the correct pre-
amble, the IMR2 device expects to see data correspond-
ing to the polarity status of the port. The corresponding
signals for each port on the transceiver should be con-
nected to a 4-to-1 multiplexer with DIR utilized as the
control lines. The multiplexer should behave as follows:
DIR[1:0] rotates through the 10
regardless of the mode of SDATA[n]. The mode of each
SDATA[n] pin can change with each cycle as transceiv-
ers are removed or inserted.
Visual Status Monitoring (LED) Support
The IMR2 device has a status port which can be con-
nected to LEDs to facilitate visual monitoring of differ-
ent repeater ports. Five port status attributes can be
monitored: Carrier Sense (CRS), Collision (COLX),
Partition (PART), Link Status (LINK), and Polarity
(POL). The status of the ports is indicated on an 8-bit
bus, LD[7:0], which is time multiplexed to show all five
attributes for up to 16 ports. BSEL is the port select pin.
When the select pin (BSEL) is LOW, LD[7:0] has the
status of ports P7 through P0. When BSEL is HIGH,
LD[3:0] has the status of P11 through P8, LD[4] has the
status of the AUI port, and LD[5] has the status of the
RAUI port. LD[7:6]is used to display the port status of
a fourth QuIET device that optionally may be shared
with another IMR2 device.
CRS, COLX, PART, LINK, and POL are the attribute se-
lect pins. When an attribute select pin is HIGH, LD[7:0]
indicates the corresponding status attribute. The Status
Monitoring port continually cycles as per 5. Each strobe
is active for 64-bit times (6.4 s). This allows a 10-per-
cent duty cycle. The following table gives the value of
LD[7:0] corresponding to the Attribute Select signal.
CRS
COLX
PART
LINK
POL
Signal
DIR[1:0]
00
01
10
11
Activity
Collision
Connected
Good
Correct
HIGH
Select Transceiver 0.
Select Transceiver 1.
Select Transceiver 2.
Select Transceiver 3.
00
No Activity
No Collision
Partitioned
None
Reversed
Action
01
LOW
11 cycle
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