Epson ARM720T Manuel D’Utilisation

The coprocessor: 

1

Decodes instructions to determine whether it can accept the 

instruction.

2

Indicates whether it can accept the instruction (by signaling 

on EXTCPA and EXTCPB).

3

Fetches any values required from its own register bank.

4

Performs the operation required by the instruction.

If a coprocessor cannot execute an instruction, the instruction takes the undefined instruction 

trap. You can choose whether to emulate coprocessor functions in software, or to design a 

dedicated coprocessor.

You can connect up to 16 coprocessors into a system, each with a unique coprocessor ID 

number. 
Some coprocessor numbers are reserved. For example, you cannot assign external 

coprocessors to coprocessor numbers 14 and 15, because these are internal to the ARM720T 

processor:

•

CP14 is the communications channel coprocessor

•

CP15 is the system control coprocessor for cache and MMU functions.

Coprocessor availability is shown in Table 8-1.

 

If you intend to design a coprocessor, send an E-mail with coprocessor in the subject 

line to info@arm.com for up to date information on coprocessor numbers that have 

already been allocated.

Table 8-1  Coprocessor availability

15

System control

14

Debug controller

13:8

Reserved

7:4

Available to users

3:0

Reserved