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Boot-up Using the HI08 Host Port

DSP56303 User’s Manual, Rev. 2

Freescale Semiconductor

6-11

6.5 Boot-up Using the HI08 Host Port

The DSP56300 core has eight bootstrap operating modes to start up after reset. As the processor

exits the Reset state the value at the external mode pins MODA/IRQA, MODB/IRQB, MODC/IRQC and

MODD

/IRQD are loaded into the Chip Operating Mode bits (MA, MB, MC and MD) of the

Operating Mode Register (OMR). These bits determine the bootstrap operating mode. Modes C,

D, E and F use the HI08 host port to bootstrap the application code to the DSP. Table 6-7

describes these modes.

The bootstrap program is factory-programmed into an internal 192-word by 24-bit bootstrap

ROM at locations $FF0000–$FF00BF of P memory. This program can load program RAM

segment from the HI08 host port. When any of the modes in the preceding table are used, the core

begins executing the bootstrap program and configures the HI08 based on the OMR mode bits.

The bootstrap program then expects the following data sequence when the user program is

downloaded from the HI08:

Three bytes (least significant byte first) indicating the number of 24-bit program words

to be loaded.

Three bytes (least significant byte first) indicating the 24-bit starting address in

P-memory to load the user's program.

The user program (three bytes, least significant byte first, for each program word).

Once the bootstrap program finishes loading the specified number of words, it jumps to the

specified starting address and executes the loaded program.

6.6 DSP Core Programming Model

The DSP56300 core treats the HI08 as a memory-mapped peripheral occupying eight 24-bit

words in X data memory space. The DSP can use the HI08 as a normal memory-mapped

peripheral, employing either standard polled or interrupt-driven programming techniques.

Separate transmit and receive data registers are double-buffered to allow the DSP and host

processor to transfer data efficiently at high speed. Direct memory mapping allows the

DSP56303 core to communicate with the HI08 registers using standard instructions and

Table 6-7. HI08 Boot Modes

Mode

MODD

MODC

MODB

MODA

HI08 Bootstrap Description

1100

ISA/DSP5630x mode

1101

HC11 non-multiplexed bus mode

1110

8051 multiplexed bus mode

1111

MC68302 bus mode

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