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Chapter 4. Interrupts Page 4-21

As shown in Table 4-16, the jump table contains a series of jump instructions, one for each individ-

ual FIFO/GPIF Interrupt source’s ISR.

4.8.1 FIFO/GPIF Autovector Coding

To employ autovectoring for the FIFO/GPIF interrupt, perform the following steps:

1. Insert a jump instruction at 0x0053 to a table of jump instructions to the various FIFO/GPIF

interrupt service routines. Make sure the jump table starts at a 0x0100-byte page boundary

plus 0x80.

2. Code the jump table with jump instructions to each individual FIFO/GPIF interrupt service rou-

tine. This table has two important requirements, arising from the format of the INT4VEC byte

(0x80-based, with the 2 LSBs set to 0); the two requirements are the following:

• It must begin on a page boundary + 0x80 (address 0xnn80).

• The jump instructions must be four bytes apart.

3. Place the interrupt service routines anywhere in memory.

4. Write initialization code to enable the FIFO/GPIF interrupt (INT4) and Autovectoring.

Table 4-16. A Typical FIFO/GPIF-Interrupt Jump Table

Table Offset Instruction

0x80 LJMP EP2PF_ISR

0x84 LJMP EP4PF_ISR

0x88 LJMP EP6PF_ISR

0x8C LJMP EP8PF_ISR

0x90 LJMP EP2EF_ISR

0x94 LJMP EP4EF_ISR

0x98 LJMP EP6EF_ISR

0x9C LJMP EP8EF_ISR

0xA0 LJMP EP2FF_ISR

0xA4 LJMP EP4FF_ISR

0xA8 LJMP EP6FF_ISR

0xAC LJMP EP8FF_ISR

0xB0 LJMP GPIFDONE_ISR

0xB4 LJMP GPIFWF_ISR

1 2 ... 106 107 108 109 110 111 112 113 114 115 116 ... 459 460

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