Vax 4000 Model 200 Technical Information PDF herunterladen (Seite 9)

1.2 Firmware Overview

Two electrically programmable read-only memory (EPROM) chips on the

KA660 CPU module contain the ﬁrmware. This ﬁrmware consists of the

following three major programs, which perform the system power-up self-

tests and diagnostics:

• A console program

• A set of self-tests for the CPU and memory

• A primary bootstrap program (VMB)

The console program receives control whenever the processor halts. In

a processor halt, processor control passes to the console program and

instruction execution continues. The standard VAX console functionality

is emulated whenever you execute a program in ROM.

Control passes to the ﬁrmware under any of the following conditions:

• You turn on the system.

• You press the Restart button.

• You assert the Q22-bus BHALT signal by pressing the Halt button.

• You enter a break when the Break Enable/Disable switch is set to

enable.

• A HALT instruction is executed.

• A fatal system error occurs.

Base System Description 1–3

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Vax 4000 Model 200 Technical Information Seite 9