Motorola 24-Bit Digital Signal Processor, DSP56000 manual Motorola

USING THE OnCE

10.11.6.1Case 1: Return To The Previous Program (Return To Normal Mode) 1. Send command WRITE PDB REGISTER, no GO, no EX (00001001)

The OnCE controller selects the PDB as the destination for serial data. Also, the OnCE controller selects the on-chip PAB register as the source for the PAB bus.

2.ACK

3.Send the 24 bits of the saved PIL (instruction latch) value.

After the 24 bits have been received, the PDB register drives the PDB. The OnCE controller causes the PIL to latch the PDB value. In this way, the PIL is restored to the same state as before entering the debug mode.

4.ACK

5.Send command WRITE PDB REGISTER, GO, EX (01101001)

The OnCE controller selects PDB as destination for the serial data to follow.

6.ACK

7.Send the 24 bits of the saved PDB value.

After the 24 bits have been received, the PDB register drives the PDB. In this way, the PDB is restored to the same state as before entering the debug mode. The EX bit causes the OnCE controller to release the chip from the debug mode and the status bits in OSCR are cleared. The GO bit causes the chip to start executing instructions.

10.11.6.2Case 2: Jump To A New Program (Go From Address $xxxx) 1. Send command WRITE PDB REGISTER, no GO, no EX (00001001)

The OnCE controller selects PDB as destination for serial data. Also, the OnCE controller selects the on-chip PAB register as the source for the PAB bus.

2.ACK

3.Send 24 bits of the opcode of a two-word jump instruction instead of the saved PIL value. After the 24 bits have been received, the PDB register drives the PDB. The OnCE controller causes the PIL to latch the PDB value. In this way, the instruction latch will contain the opcode of the jump instruction which will cause the change in the program flow.

4.ACK

5.Send command WRITE PDB REGISTER, GO, EX (01101001) The OnCE controller selects PDB as destination for serial data.

6.ACK

7.Send 24 bits of the jump target absolute address ($xxxxxx).

After 24 bits have been received, the PDB register drives the PDB. In this way, the PDB contains the second word of the jump as required for the jump instruction ex-

MOTOROLA ON-CHIP EMULATION (OnCE) 10 - 27