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Table A.2 shows the ARM922T coprocessor interface signals.
Table A.2. Coprocessor interface signals
Name | Direction | Description |
|---|---|---|
CHSDE[1:0] | Input | Coprocessor handshake decode. The handshake signals from the Decode stage of the coprocessor pipeline follower. |
CHSEX[1:0] | Input | Coprocessor handshake execute. The handshake signals from the Execute stage of the coprocessor pipeline follower. |
CPCLK | Output | Coprocessor clock. This clock controls the operation of the coprocessor interface. |
CPDOUT[31:0] | Output | Coprocessor data out. The coprocessor
data bus for transferring |
CPDIN[31:0] | Input | Coprocessor data in. The coprocessor
data bus for transferring |
CPEN | Input | Coprocessor data out enable. When tied LOW, the CPID and CPDOUT buses are held stable. When tied HIGH, the CPID and CPDOUT buses are enabled. It is expected that this pin is used statically. |
CPID[31:0] | Output | Coprocessor instruction data. This is the coprocessor instruction data bus used for transferring instructions to the pipeline follower in the coprocessor. |
CPLATECANCEL | Output | Coprocessor late cancel. When a coprocessor instruction is being executed, if this signal is HIGH during the first Memory cycle, the coprocessor instruction must be canceled without having updated the coprocessor state. |
nCPMREQ | Output | Not coprocessor memory request. When LOW on a rising CPCLK edge and nCPWAIT LOW, the instruction on CPID enters the Decode stage of the coprocessor pipeline follower. The second instruction previously in the Decode stage of the pipeline follower enters its Execute stage. |
CPPASS | Output | Coprocessor pass. This signal indicates that there is a coprocessor instruction in the Execute stage of the pipeline, and it must be executed. |
CPTBIT | Output | Coprocessor Thumb bit. If HIGH, the coprocessor interface is in Thumb state. |
nCPTRANS | Output | Not coprocessor translate. When LOW, the coprocessor interface is in a nonprivileged mode. When HIGH, the coprocessor interface is in a privileged mode. The coprocessor samples this signal on every cycle when determining the coprocessor response. |
nCPWAIT | Output | Not coprocessor wait. The coprocessor clock CPCLK is qualified by nCPWAIT to allow the ARM922T processor to control the transfer of data on the coprocessor interface. nCPWAIT changes while CPCLK is HIGH. |
For more information on the coprocessor interface see Chapter 7 Coprocessor Interface.