Chapter 4: Boot Rom Functions - HP 330 Service Information Manual

Boot ROM Functions
4
Introduction
When the computer is turned on, three Boot ROM instruction sets are executed by the CPU.
Other Series 300 computers have similar Boot ROM functions. Information on the following
functions is in this chapter.
• Power-Up Sequence.
• Self.-Tests.
• Booting Operating System.
Power-Up Sequence
Power-up Overview
These events happen when the computer is turned on and the Boot ROM code is executed by
the CPU for the power-up sequence. Tests and initialization of devices are:
• Necessary for operation of Boot ROM code (CPU, Boot ROM, RAM).
• Used for interaction with user during power-up (display, keyboard, and some I/O) second.
• Used for booting (HP-IB, and SRM interface card).
Note
Exhaustive testing of computer hardware not used by the boot ROM
should be done using the Series 300 Test Tools and/or by some other
means. The Boot ROM's self-test code is not a component level diag-
nostzc tool.
Table 4-1 shows the flow of events for the Power- Up Sequence. It shows everything that happens
between power-up and the start of the boot scanner. This includes self-test and initialization.
During the Power-Up Sequence, the LEDs and the monitor's display are used to tell what is
happening. The section that follows discusses how the LEDs are used.
Pressing
[Beset
I
will re-start the Power-Up Sequence. RESETs are locked-out or deferred during
all mass storage operations to prevent leaving devices stranded in unknown states.
On power-·up, the CPU is initialized and executes the Power-Up Sequence instructions in the
Boot
RO~1.
The Power-Up Sequence is shown in Table 4-2.
Boot ROM Functions
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