3.3.1. CLK and CLKEN

CLK is the master clock for the ETM7. The ETM7 only uses the rising edge of CLK, so CLK is the inverse of MCLK when used with an ARM7TDMI, and CLK when used with an ARM7TDMI-S.

CLKEN is a synchronous enable for CLK. All ARM7 interface signals are sampled on the rising edge of CLK when CLKEN is HIGH, and all trace port outputs are generated off the rising edge of CLK.

Note

The trace port outputs can change during clock cycles when CLKEN is LOW. You must avoid dynamically stretching or gating the CLK signal, because this prevents the use of cycle-accurate tracing.

Connecting to an ARM7TDMI-S

You must connect the ETM7 signals, CLK and CLKEN, directly to the same signals that drive the ARM7TDMI-S CLK and CLKEN.

Connecting to an ARM7TDMI

When connecting ETM7 directly to an ARM7TDMI, you must connect CLK to the inverse of MCLK, and CLKEN to nWAIT inputs.

Connecting to an ARM720T

When connecting ETM7 to an ARM720T, you must connect CLK to ETMCLK and CLKEN to the ETMCLKEN ARM720T output.

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