3.6.2. Boolean combinations for defining events

ETM event logic introduced the ETM concept of an event as a logical combination of two event resources, used to control the basic transitions in the ETM. This section summarizes where you require event descriptions to program the ETM registers, and then describes how you define an ETM event.

Where events are used

The following sections use event definitions, as described in Defining events:

Defining events

If A is defined as the first resource match and B as the second match, an event is defined as a function of A and B. The functions and their bit encodings are listed in Table 3.90.

Table 3.90. Boolean function encoding for events

Encoding

Function

b000

A

b001

NOT(A)

b010

A AND B

b011

NOT(A) AND B

b100

NOT(A) AND NOT(B)

b101

A OR B

b110

NOT(A) OR B

b111

NOT(A) OR NOT(B)


A and B are identified with two 7-bit fields. See Resource identification for the exact resource encoding.

An event is encoded in three fields using 17 bits in total, as Table 3.91 shows. Two fields encode the two event resources, see Table 3.89 and Table 3.88. The third field specifies the Boolean operation to be applied to them, see Table 3.90.

Table 3.91. Event encoding

Bit

Description

[16:14]

Boolean function

[13:7]

Resource B

[6:0]

Resource A


Figure 3.73 shows event and resource encoding.

Figure 3.73. Event and resource encoding

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Note

To permanently enable or disable an event, you must specify:

  • Resource A as the hard-wired input (type b110, index 15)

  • the boolean function as either A (enable) or Not (A) (disable).

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