3.3 Reading the Application ID Word

The Application ID Word is stored at the address 0x800BFE in executive code memory. To read this memory location, you must use the SIX control code to move this program memory location to the VISI register. Then, the REGOUT control code must be used to clock the contents of the VISI register out of the device. The corresponding control and instruction codes that must be serially transmitted to the device to perform this operation are provided in Table 3-1.

After the programmer has clocked out the Application ID Word, it must be inspected. If the Application ID has the value 0xDF, the Programming Executive is resident in memory, and the device can be programmed using the mechanism described in Device Programming – Enhanced ICSP. However, if the Application ID has any other value, the Programming Executive is not resident in memory; it must be loaded into memory before the device can be programmed. The procedure for loading the Programming Executive to memory is described in Programming the Programming Executive to Memory.

Table 3-1. Serial Instruction Execution for Reading the Application ID Word
Command (Binary)	Data (Hex)	Description
Step 1: Exit the Reset vector.
`0000` `0000` `0000` `0000` `0000` `0000` `0000`	`000000` `000000` `000000` `040200` `000000` `000000` `000000`	`NOP` `NOP` `NOP` `GOTO 0x200` `NOP` `NOP` `NOP`
Step 2: Initialize the TBLPAG register and the Read Pointer (W0) for the TBLRD instruction.
`0000` `0000` `0000` `0000` `0000` `0000` `0000` `0000` `0000` `0000` `0000`	`200800` `8802A0` `20BFE0` `20FCC1` `000000` `BA0890` `000000` `000000` `000000` `000000` `000000`	`MOV #0x80, W0` `MOV W0, TBLPAG` `MOV #0xBFE, W0` `MOV #VISI, W1` `NOP` `TBLRDL [W0], [W1]` `NOP` `NOP` `NOP` `NOP` `NOP`
Step 3: Output the VISI register using the `REGOUT` command.
`0001`	`<VISI>`	Clock out contents of the VISI register.