ARM1156T2F-S™ Technical Reference Manual 15.1.5. Coprocessor interface

15.1.5. Coprocessor interface

This interface enables an ETM to monitor a sub-set of CP14 and CP15 operations. Rather than using the external coprocessor interface, the core provides a dedicated, cut-down coprocessor interface similar to that used by the debug logic.

Table 15.8 shows the coprocessor interface signals.

Table 15.8. Coprocessor interface signals

Signal name	Direction	Description	Qualified by	Reg bound
ETMCPENABLE	Output	Interface enable. ETMCPWRITE and ETMCPADDRESS are valid this cycle, and the remaining signals are valid two cycles later.	None	Yes
ETMCPCOMMIT	Output	Commit. If this signal is LOW two cycles after ETMCPENABLE is asserted, the transfer is canceled and must not take any effect.	ETMCPENABLE +2	Yes
ETMCPWRITE	Output	Read or write. Asserted for write.	ETMCPENABLE	Yes
ETMCPADDRESS[14:0]	Output	Register number.	ETMCPENABLE	Yes
ETMCPRDATA[31:0]	Input	Read data.	ETMCPCOMMIT	Yes
ETMCPWDATA[31:0]	Output	Write value.	ETMCPCOMMIT	Yes

A complete transaction takes three cycles. The first and last cycles can overlap, giving a sustained rate of one every two cycles.

Note

Because current Embedded Trace Macrocells (ETMs) do not use the ETMCPRDATA[31:0] signal you must ensure that the signal is tied off to 0x00000000.

Only the following instructions are presented by the coprocessor interface:

MRC p14, 1, <Rd>, c0, <CRm>, <op2>

MCR p14, 1, <Rd>, c0, <CRm>, <op2>

MCR p15, 0, <Rd>, c13, c0, 1

The format of the ETMCPADDRESS[14:0] signals are shown in Figure 15.1.

Figure 15.1. ETMCPADDRESS format

In Figure 15.1, the CP bit is 0 for CP14 or 1 for CP15.

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