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Principles of Operation
CL LED PAIR. The event indicated by the CL LED pair is the occurrence of the Signal Quality Error
(Collision) signal on the Control In pair of the AUI cable. When the HP 30241A MAU, whether it is
transmitting to the coaxial cable or not, detects a collision on the cable, it sends the SQE signal to the
LANIC on the CI pair. SQE is signalled by a 10 MHz signal on the CI pair. The event begins when the
first transition is received at the LANIC, and ends 200 nsec after the last transition is received.
The SQE heartbeat, which is a short burst of 10 MHz signal on the CI pair after each transmission by the
LANIC on DO, does not cause the E LED to blink, although it does cause the L LED to light for
approximately 1 usec, which is too short to be seen. Likewise, no collision occurring on the network
within 5.3 usec of cessation of transmission by the LANIC will light the E LED. The SQE heartbeat is
blocked from triggering the
E
LED so that the CL LEDswill indicate the frequency of collisions
occurring on the network.
CR LED PAIR. The event indicated by the CR LED pair is the reception of data on the Data In pair in
the AUI cable, or the occurrence of the collision event described above. The event begins when the first
data transition arrives on the AUI DI pair, or when the collision event begins, whichever occurs first. The
event ends 200 nsec after the last data transition on the DI pair, or when the collision event ends,
whichever occurs last.
H THROUGH NAND
*
LEDs.. When the LANIC has been reset either by power-up of the system or by
the operating software, all eight of the MPU activity indicators (LEDs H through Nand
*)
will be on
continuously. This indicates that the MPU is not executing. Additionally, the VP LED will be off, which
indicates that the MAU is not powered. The other AUI activity indicator LEDs will all be off.
After the LANIC has successfully passed self -test, and the pass code pattern has been displayed as
required, the
*
LED will be off, and the other seven MPU activity indicator LEDs will now indicate the
MPU activity. The
*
LED being off indicates that the H-N LEDs are to be interpreted as individual
activity indicators according to their two-letter mnemonics. (See the following paragraphs.)
TX, RX, MN, DL, RO,
Q,
AND IT LEDs. When self-test passes, the SPU is interrupted and notified of
the event. Between the time that this interrupt is given and the time when the SPU begins to access the
LANIC, the RO and Q LEDs will be lit. This indicates that the LANIC is executing ROM code and is
quiescent, while waiting for the SPU to take control. In addition, the VP LED will be lit, indicating that
the MAU is powered. Any activity on the network coaxial cable will be indicated by the state of the CL
and CR LED pairs. The LANIC will never transmit in this state, and therefore, the DO LED pair will
remain inactive.
When the SPU prepares the LANIC for operation, it first must download the operating firmware from
system memory to the LANIC. When this process begins, the DL LED turns on, and the Q and IT LEDs
will go off. After each download command, the Q LED lights for a few milliseconds.
At least seven
download commands occur, but they may not be separately distinguishable. However, the pattern that
occurs on one working system will occur on all other working systems, so if suspicious, compare the
download pattern on the suspected system with a system that works.
After the download is complete, the SPU will instruct the MPU to begin to execute the downloaded
firmware. When this occurs, the RO and DL LEDs will go off. The Q and IT LEDs will turn on.
Feb 85
3-16
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