HP 300

Test and Boot Code Segment
This section explains the sequence the CPU executes Boot ROM test list vectors and loops
through self-test if continuous self-test is enabled.
The Test List (like the Boot List) is a temporary structure used by the Boot ROM to allow
upgrades
and extensions. The Test List is a linked list whose elements are vectors which point
to test code for various devices. The test and/or initialization code for a given devices is generally
of
the format:
Indicate on LEDs the device being tested.
If the device is present THEN
F the test initialization fails THEN indicate the failure
ELSE indicate the presence of thedevice.
A step-by-step list of
what happens in this Boot ROM code segment is explained. As before,
each
step is preceded by an indication of that step on the LEDs. The test list for the Boot ROM
is as follows:
1. Which Processor:
An exception format word
is pushed onto the stack, and an RTE is executed. The state
of the stack indicates whether or not the processor is an MC68000
1
.
If the CPU was not
an MC68000, then a divide by zero is executed and the stack is checked to distinguish
between
an MC68010 and an MC68020 CPU. The Boot ROM does not distinguish between
an MC68010 and an MC68012 CPU. Sysflag2 is set up accordingly.
2. Initialize Timer:
The Boot ROM determines if there is a timer on the processor. If there is one, then it
is tested and initialized, and a bit is set in sysflag2 to indicate its presence. If one is not
present, or if a failure occurred, then the Boot ROM halts with 0516 on the LEDs.
3. Initialize Monitor:
The Boot ROM determines if a RAM Monitor is present at 88000016. If there is one, then
its presence is indicated in F _AREA.
4. Reset I/O:
A RESET instruction is executed to clear all I/O. The Boot ROM sets up the processor's
keyboard electronics, if present,
to ensure that its timer does not lose time. Keyboard
electronics on an accessory card are not set up.
5. Initialize and Test Display:
1 Much of this Boot ROM code is used in other HP 9000 Series 200 computers using the MC68000 CPU. In this case, a
MC68000CPU will not be found and the CPU will look for a MC68010 or MC68020 CPU on the processor board.
86 Boot ROln Functions
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