Serial Control Bus - DEC 4000 600 series Owner's Manual

CPU Subsystem
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The serial control bus is a two-conductor serial interconnect bus
Serial Control
that is independent of the system bus. The serial control bus
Bus
connects the following modules:
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The serial control bus is used by the system to communicate
with the main interfaces on the operator control panel and power
system controller, and with the 256 x 8 error log EEPROM
devices on the CPU, I/O, and memory modules.
The serial control bus is also used by the system for maintenance
and control functions, such as power-up and power-down
sequencing, error-logging, and error-reporting.
Power Subsystem
The power subsystem is a universal supply that automatically
Components
selects the correct operational voltage range. Some elements of
the supply are distributed, others are centralized and modular.
Power for the backplanes is provided by the centralized power
source. Fixed-media storage devices are powered by DC-DC
converters (local disk converters) included in each storage
compartment.
7–8 Learning More About Your System
One asynchronous serial line unit (SLU) dedicated to the
console subsystem.
One additional asynchronous SLU with modem control.
Serial control bus controller for communications with other
components of the system.
CPUs
I/O module
Memory modules
Power system controller (PSC)
Operator control panel (OCP)