Epson ARM.POWERED ARM720T - Manual (Page 129)

8: Coprocessor Interface
ARM720T CORE CPU MANUAL EPSON 8-9
8.5 Connecting coprocessors
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).
8.5.1 Connecting a single coprocessor
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
. Note:
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.
8.5.2 Connecting multiple coprocessors
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
Signal Connection
CPnCPI 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
AMBA
in
te
rf
a
c
e
CPDIN
CPDOUT