C167CS datasheet(238/517 Pages) INFINEON

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C167CS

Derivatives

The General Purpose Timer Units

User’s Manual

10-10

V2.0, 2000-07

The incremental encoder can be connected directly to the C167CS without external

interface logic. In a standard system, however, comparators will be employed to convert

the encoder’s differential outputs (e.g. A, A) to digital signals (e.g. A). This greatly

increases noise immunity.

Note: The third encoder output Top0, which indicates the mechanical zero position, may

be connected to an external interrupt input and trigger a reset of timer T3 (e.g. via

PEC transfer from ZEROS).

Figure 10-7

Connection of the Encoder to the C167CS

For incremental interface operation the following conditions must be met:

• Bitfield T3M must be ‘110B’.

• Both pins T3IN and T3EUD must be configured as input, i.e. the respective direction

control bits must be ‘0’.

• Bit T3UDE must be ‘1’ to enable automatic direction control.

The maximum counting frequency which is allowed in incremental interface mode is

fCPU/16. To ensure that a transition of any input signal is correctly recognized, its level

should be held high or low for at least 8

fCPU cycles before it changes. As in Incremental

Interface Mode two input signals with a 90° phase shift are evaluated, their maximum

input frequency can be

fCPU/32.

In Incremental Interface Mode the count direction is automatically derived from the

sequence in which the input signals change, which corresponds to the rotation direction

of the connected sensor. Table 10-7 summarizes the possible combinations.

Table 10-7

GPT1 Core Timer T3 (Incremental Interface Mode) Count Direction

Level on respective

other input

T3IN Input

T3EUD Input

Rising

Falling

Rising

Falling

High

Down

Low

Down

MCS04372

Encoder

C167CR

T3Input

Interrupt

Signal

Conditioning

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