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The
TMS32020/C25
Inverse
Assembler
HP E2418A
I
Note
ID
The JACK signal and the CLKOUTl signals are used by the inverse
assembler to distinguish an instruction fetch from an operand read.
When CLKOUTl is low, a low JACK indicates an Interrupt
Acknowledge. When CLKOUTl is high, a high JACK indicates
Instruction Acquisition.
The inverse assembler examines the value in the ADDR field at each
state line to determine if the TMS32020/C25 microprocessor has
acknowledged an interrupt (address < lF hex). The JACK signal is
not used to determine when an interrupt has been acknowledged.
The TMS32020/C25 microprocessor does not provide enough status
information for the inverse assembler to pick out the first word of an
opcode fetch from a series of program reads. To ensure correct
disassembly, you may need to point to the 16-bit word that contains the
first word of an opcode fetch. Once synchronized, the inverse
assembler
will disassemble from this point through the end of the
screen. Use the following steps to point to the first word of an opcode
fetch:
1. Select a line on the display that you know contains the first word
of an opcode fetch.
2. Roll this line to the top of the screen.
The cursor location is not the top of the display. In figure 2-2, line 0 is
at the top of the display.
3. Select the "Invasm" field at the top of the display.
Rolling the display up
will inverse assemble the lines as they appear on
the bottom of the display. If you jump to another area of the display by
entering a new line number, you may need to re-synchronize the
inverse assembler by repeating steps 1 through 3.
Each time you inverse assemble a block of memory, the analyzer
will
keep that block in the inverse assembled condition. You can inverse
assemble several different blocks in the analyzer memory, but activity
between those blocks
will not be inverse assembled.
TMS32020/C25 Preprocessor Interface
Analyzing the Intel TMS32020/C25
2-5
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