Led Indicators - HP 10343B Operating Manual

LED Indicators
Two LED light bars of 10 LEDs each are used as front panel indicators
for static conditions of the bus (see figure 2-11).
• One group for Data; and
• One group for Status.
For Data, data bits 0 through 7, Parity, and a Parity Error LED light is
provided. The Parity Error is not one of the SCSI signal lines, but is
generated by internal hardware of the interface when a parity error occurs
and the front panel State Parity Error switch is on.
Note
There are two parity lights on the Data tight bar. The Data Parity
bit is part of the SCSI bus. The Parity Error is generated by the
interface when there is an Odd Parity Error. This tight comes on
only if the Parity Selector Switch is on and a parity error is
detected.
Nine SCSI Status lines are shown on the other LED light bar. These
include I/O, C/D, MSG, and the SCSI phases.
Also, an internal line that is unique to the interface is on the tenth LED.
This LED is labeled as INF for "Information Transfer." INF is on when
the bus is in the Data, Command, Status, or Message phases and turns off
when the bus goes into the Bus Free State. This indicator remains off
during the Arbitration, Select, and Reselect phases.
SCSI Bus Preprocessing
2-28