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Blocks Outside the DSP56800 Core

2.3 Blocks Outside the DSP56800 Core

The following blocks are optionally found on DSP56800-based DSP chips and are considered peripheral and memory blocks, not part of the DSP56800 core. These and other blocks are described in greater detail in the appropriate chip-specific user’s manual. Figure 2-3 shows an example DSP56800-based device. Note that this device uses the Motorola IP-BUS interface to connect to peripherals. Other chips may use the PGDB peripheral bus.

 

 

Program

 

Data

On-Chip

PLL

 

 

Expansion

 

RAM/ROM

 

RAM/ROM

 

 

Expansion

 

Expansion

Area

Clock

 

 

 

 

 

Generator

 

 

XDB2

 

 

 

 

 

Peripheral

 

 

 

 

Modules

 

 

 

 

 

 

 

XAB1

 

 

 

 

Address

XAB2

 

 

 

Generation

 

 

 

PAB

 

 

 

 

Unit

DSP

 

 

 

 

 

 

 

 

 

16-Bit

 

 

Internal

 

 

Core

 

IP-BUS

PDB

 

 

 

Data Bus

CGDB

 

 

 

Bridge

Switch

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Data ALU

 

 

Program

 

16 x 16 + 36

36-Bit MAC

JTAG/

 

Controller

 

Three 16-Bit Input Registers

 

 

OnCETM

 

 

 

 

 

 

Two 36-Bit Accumulators

 

 

 

IRQB

 

 

16-Bit Data Bus

 

 

IRQA

 

 

 

 

 

 

 

 

 

RESET

 

 

 

Figure 2-3. Sample DSP56800-Family Chip Block Diagram

2.3.1 External Data Memory

External data memory (data RAM, data ROM, or both) can be added around the core on a chip. Addresses are received from the XAB1 and XAB2. Data transfers occur on the CGDB and XDB2. One read, one write, or two reads can be performed during one instruction cycle using the internal data memory. Depending upon the particular on-chip peripherals found on a device, some portion of the data address space may be reserved for peripheral registers, and not be accessible as external data memory. A total of 65,536 memory locations can be addressed.

Core Architecture Overview

2-7

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