Epson ARM720T User Manual

A coprocessor in a system based on an ARM720T processor must have 32-bit connections to:

•

transfer data from memory (instruction stream and LDC)

•

write data from the ARM720T processor (MCR)

•

read data to the ARM720T processor (MRC).

You can connect a single coprocessor directly to the coprocessor interface of the ARM720T 

processor without any additional logic, as shown in Figure 8-5. EXTCPDBE must be driven 

HIGH by the external coprocessor when it drives data on EXTCPDOUT.

Figure 8-5  Example coprocessor connections

 

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If you are building a system with an ETM7 and an ARM720T core, you must 

directly connect the following buses:
•

ETM7 input RDATA[31:0] to the ARM720T processor output 

ETMRDATA[31:0]

ETM7 input WDATA[31:0] to the ARM720T processor output 

ETMWDATA[31:0]. 

This enables the ETM to correctly trace coprocessor instructions.

If you have multiple coprocessors in your system, connect the handshake signals as shown in 

Table 8-3.

You must also multiplex the output data from the coprocessors.

Table 8-3  Handshake signal connections

Connect this signal to all coprocessors present in the system

CPA and CPB

The individual CPA and CPB outputs from each coprocessor 
must be ANDed together, and connected to the EXTCPA and 
EXTCPB inputs on the ARM720T processor

ARM720T (Rev 4)

processor

External coprocessor

Memory

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