Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

848

predefined value is configurable and corresponds to (MAXFILT + 1) * t

MCK

 ns. After being filtered there is no 

reason to have two edges closer than (MAXFILT + 1) * t

MCK

 ns under normal mode of operation.

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 the POSEN bit is set in the TC_BMR, the motor axis position is processed on channel 0 (by means of the 

PHA, PHB edge detections) and the number of motor revolutions are recorded on channel 1 if the IDX signal is 

provided on the TIOB1 input. The position measurement can be read in the TC_CV0 register and the rotation 

measurement can be read in the TC_CV1 register.
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.

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