EXCEPTION PROCESSING STATE (INTERRUPT PROCESSING)
MOTOROLA
PROCESSING STATES
7 - 29
6. The fast interrupt returns without an RTI.
7. Normal instruction fetching resumes using the PC following the completion of
the fast interrupt routine.
8. A fast interrupt is not interruptible.
9. A JSR instruction within the fast interrupt routine forms a long interrupt routine.
10. The primary application is to move data between memory and I/O devices.
The execution of a long interrupt routine always conforms to the following rules:
1. A JSR to the starting address of the interrupt service routine is located at one
of the two interrupt vector addresses.
2. During execution of the JSR instruction, the PC and SR are stacked. The inter-
rupt mask bits of the SR are updated to mask interrupts of the same or lower
priority. The loop flag, trace bit, double precision multiply mode bit, and scaling
mode bits are reset.
3. The first instruction word of the next interrupt service (of higher IPL) will reach
the decoder only after the decoding of at least four instructions following the
decoding of the first instruction of the previous interrupt.
4. The interrupt service routine can be interrupted — i.e., nested interrupts are
supported.
5. The long interrupt routine, which can be any length, should be terminated by
an RTI, which restores the PC and SR from the stack.
Figure 7-10 illustrates the effect of a long interrupt routine on the instruction pipeline. A
short JSR (a JSR with 12-bit absolute address) is used to form the long interrupt routine.
For this example, word 6 of the long interrupt routine is an RTI. The point at which inter-
rupts are re-enabled and subsequent interrupts are allowed is shown to illustrate the
non-interruptible nature of the early instructions in the long interrupt service routine.
Either one of the two instructions of the fast interrupt can be the JSR instruction that
forms the long interrupt. Figure 7-11 and Figure 7-12 show the two possible cases. If the
first fast interrupt vector instruction is the JSR, the second instruction is never used.
A REP instruction and the instruction that follows it are treated as a single two-word
instruction, regardless of how many times it repeats the second instruction of the pair.
Instruction fetches are suspended and will be reactivated only after the LC is decre-
Summary of Contents for DSP56K
Page 12: ...xii LIST of TABLES MOTOROLA List of Tables Continued Table Page Number Title Number ...
Page 13: ...MOTOROLA DSP56K FAMILY INTRODUCTION 1 1 SECTION 1 DSP56K FAMILY INTRODUCTION ...
Page 31: ...MOTOROLA DATA ARITHMETIC LOGIC UNIT 3 1 SECTION 3 DATA ARITHMETIC LOGIC UNIT ...
Page 50: ...DATA ALU SUMMARY 3 20 DATA ARITHMETIC LOGIC UNIT MOTOROLA ...
Page 51: ...MOTOROLA ADDRESS GENERATION UNIT 4 1 SECTION 4 ADDRESS GENERATION UNIT ...
Page 77: ...MOTOROLA PROGRAM CONTROL UNIT 5 1 SECTION 5 PROGRAM CONTROL UNIT ...
Page 124: ...INSTRUCTION GROUPS 6 30 INSTRUCTION SET INTRODUCTION MOTOROLA ...
Page 125: ...MOTOROLA PROCESSING STATES 7 1 SECTION 7 PROCESSING STATES STOP WAIT EXCEPTION NORMAL RESET ...
Page 167: ...STOP PROCESSING STATE MOTOROLA PROCESSING STATES 7 43 ...
Page 168: ...STOP PROCESSING STATE 7 44 PROCESSING STATES MOTOROLA ...
Page 169: ...MOTOROLA PORT A 8 1 SECTION 8 PORT A ...
Page 176: ...PORT A INTERFACE 8 8 PORT A MOTOROLA ...
Page 177: ...MOTOROLA PLL CLOCK OSCILLATOR 9 1 SECTION 9 PLL CLOCK OSCILLATOR x x d Φ VCO ...
Page 191: ...10 2 ON CHIP EMULATION OnCE MOTOROLA SECTION 10 ON CHIP EMULATION OnCE ...
Page 218: ...USING THE OnCE MOTOROLA ON CHIP EMULATION OnCE 10 29 ...
Page 604: ...INSTRUCTION ENCODING A 338 INSTRUCTION SET DETAILS MOTOROLA ...
Page 605: ...MOTOROLA BENCHMARK PROGRAMS B 1 APPENDIX B BENCHMARK PROGRAMS T T T T T P1 P3 P2 P4 T T T ...
Page 609: ...BENCHMARK PROGRAMS MOTOROLA BENCHMARK PROGRAMS B 5 ...
Page 611: ...BENCHMARK PROGRAMS MOTOROLA BENCHMARK PROGRAMS B 7 ...
Page 613: ...BENCHMARK PROGRAMS MOTOROLA BENCHMARK PROGRAMS B 9 ...
Page 615: ...BENCHMARK PROGRAMS MOTOROLA BENCHMARK PROGRAMS B 11 ...