Overview

If the interrupt service routine for an interrupt is too large to fit in a single fetch packet, a branch to the location of additional interrupt service routine code is required. Figure 5−3 shows that the interrupt service routine for INT4 was too large for a single fetch packet, and a branch to memory location 1234h is required to complete the interrupt service routine.

Note:

The instruction B LOOP branches into the middle of a fetch packet and processes code starting at address 1234h. The CPU ignores code from address 1220h−1230h, even if it is in parallel to code at address 1234h.

Figure 5−3. Interrupt Service Table With Branch to Additional Interrupt Service Code Located Outside the IST

The interrupt service routine

for INT4 includes this

7-instruction extension of

the interrupt ISFP.

1220h

 

 

1224h

 

 

1228h

122Ch

 

 

1230h

 

 

LOOP: 1234h

Instr9

 

 

1238h

B IRP

 

 

123Ch

Instr11

1240h

 

 

Instr12

 

 

1244h

Instr13

 

 

1248h

Instr14

 

 

124Ch

Instr15

 

 

1250h

 

 

1254h

 

 

1258h

 

 

125Ch

 

 

000h

020h

040h

060h

080h

0A0h

0C0h

0E0h

100h

120h

140h

160h

180h

1A0h

1C0h

1E0h

IST

RESET ISFP

NMI ISFP

Reserved

Reserved

INT4 ISFP

INT5 ISFP

INT6 ISFP

INT7 ISFP

INT8 ISFP

INT9 ISFP

INT10 ISFP

INT11 ISFP

INT12 ISFP

INT13 ISFP

INT14 ISFP

INT15 ISFP

Additional ISFP for INT4

Additional ISFP for INT4

Program memory

ISFP for INT4

080h Instr1

084h Instr2

088h B LOOP

08Ch Instr4

090h Instr5

094h Instr6

098h Instr7

09Ch Instr8

5-8

Interrupts

SPRU733

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Texas Instruments TMS320C67X/C67X+ DSP manual 1238h