3.5.5. Using the system options bus

The system options bus is an 8-bit input bus called SYSOPT[7:0]. This is provided on ETM7 Rev 1. It allows you to specify whether certain trace features, such as half-rate clocking, are implemented on the ASIC. You must tie each of the bits of the bus to either GND or VDD, depending on the features supported. The trace debug tools should read the state of this input bus using the JTAG interface, and adapt the user options offered accordingly. The bit meanings of the SYSOPT bus are shown in Table 3.2.

Table 3.2. SYSOPT bus settings

Bit numberDescription
7If HIGH, demultiplexed trace data format is supported.
6If HIGH, multiplexed trace data format is supported.
5If HIGH, normal trace data format is supported.
4If HIGH, full-rate clocking is supported.
3If HIGH, half-rate clocking is supported.
2:0Maximum port width supported:000 = 4-bit only001 = 4/8-bit only010 = 4/8/16-bit.


If the correct input is not supplied to the SYSOPT bus, the operation of the trace tools might be unreliable.

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