SDA6000 Datasheet, PDF (161/380 Pages) Infineon Technologies AG – Teletext Decoder with Embedded 16-bit Controller

SDA 6000
Peripherals
generated each time a count action for timer T3 occurs. Count direction, changes in the
count direction and count requests are monitored through the status bits T3RDIR,
T3CHDIR and T3EDGE in register T3CON. T3 is modified automatically according to the
speed and the direction of the incremental encoder. Therefore, the contents of the T3
timer always represents the encoder’s current position.
Table 7-4 Core Timer T3 (Incremental Interface Mode) Input Edge Selection
T3I
000
001
010
Triggering Edge for Counter Increment/Decrement
None. Counter T3 stops.
Any transition (rising or falling edge) on T3IN.
Any transition (rising or falling edge) on T3EUD.
011
1XX
Any transition (rising or falling edge) on any T3 input (T3IN or T3EUD).
Reserved. Do not use this combination.
The incremental encoder can be connected directly to the microcontroller 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 T0, which indicates the mechanical zero position, may
be connected to an external interrupt input and trigger a reset of timer T3.
A
A
A
T3 Input
External B
Encoder B
B
T3 Input Microcontroller
T0
T0
T0
Interrupt
Signal Conditioning
UED11136
Figure 7-6 Interfacing the Encoder to the Microcontroller
For incremental interface operation the following conditions must be met:
• The T3M bit field must be ‘110_B’ or ‘111_B’.
• Pins associated with lines T3IN and T3EUD must be configured as input.
• The T3UDE bit must be set to enable automatic direction control.
Users Manual
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2000-06-15