Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 780

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

to (MAXFILT+1) * tMCK ns. After being filtered there is no reason to have 2 edges closer than (MAXFILT+1) * tMCK ns
under normal mode of operation. In the instance an anomaly occurs, a quadrature error is reported on QERR flag on
TC_QISR register.

MAXFILT must be tuned according to several factors such as the system clock frequency (MCK), type of rotary sensor
and rotation speed to be achieved.

When POSEN is set in TC_BMR register, position is processed on channel 0 (by means of the PHA,PHB edge
detections) and motor revolutions are accumulated in channel 1 timer/counter and can be read through TC_CV0 and/or
TC_CV1 register if the IDX signal is provided on TIOB1 input.

Channel 0 and 1 must be configured in capture mode (WAVE = 0 in TC_CMR0).

In parallel, the number of edges are accumulated on timer/counter channel 0 and can be read on the TC_CV0 register.

Therefore, the accurate position can be read on both TC_CV registers and concatenated to form a 32-bit word.

The timer/counter channel 0 is cleared for each increment of IDX count value.

Depending on the quadrature signals, the direction is decoded and allows to count up or down in timer/counter channels
0 and 1. The direction status is reported on TC_QISR register.

MCK

MAXFILT = 2

PHA

PHB

Abnormally formatted optical disk strips (theoretical view)  

PHA

PHB

strip edge inaccurary due to disk etching/printing process 

resulting PHA, PHB electrical waveforms

PHA

PHB

Even with an abnorrmaly formatted disk, there is no occurence of  PHA, PHB switching at the same time.

QERR

duration < MAXFILT