MAS281 datasheet(16/55 Pages) DYNEX

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MAS281

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Figure 7: Pending Interrupt Register Bit Assignments

Figure 8: Fault Register Bit Assignments

3.6.2 USING BPT

The Hold state may also be entered by executing a BPT

instruction with Console present indicated in the Configuration

Word. On encountering a BPT instruction, the processor reads

the Configuration Word to check for the presence of a

Console. If a Console is indicated, the microsequencer

branches to the microcode BPT Hold service routine. This

routine decrements IC once, drops HLDAKN low, and enters

the Hold state.

To release the MAS281 from a BPT initiated Hold state, the

HOLDN input must be pulsed low in accordance with the

timing diagrams in Section 6.0. When HOLDN returns high, the

Hold state will be released on the following SYNCN high-to-low

transition. The instruction pipeline is then refilled and

instruction execution resumes with the first instruction loaded

into the pipeline.

3.6.3 SINGLE-STEPPING

Software can be single-stepped through the proper use of

the HOLDN input and the BPT instruction. Use the BPT

instruction to mark the beginning of the section of code which

will be stepped through. Pulse HOLDN low to release the BPT

initiated Hold state and then pull HOLDN low again during the

two subsequent SYNCN cycles that refill the instruction

pipeline. When the first instruction following Hold release

completes execution, the module will once again enter the

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