AT32UC3L064-D3HES ATMEL [ATMEL Corporation], AT32UC3L064-D3HES Datasheet - Page 662

• Manufacturer Part Number: AT32UC3L064-D3HES
• Manufacturer: ATMEL [ATMEL Corporation]

28.6.7
28.6.8
28.6.9
32099D–06/2010
Synchronization
Resistive Drive
Discharge Current Source
9, 3, 4, 5, 6, 7, 8, 9, 3, 4, etc. MAXDEV must not exceed the value of (2(DIV+1)), or undefined
behavior will occur.
To prevent interference from the 50 or 60Hz mains line the CAT can trigger acquisition on the
SYNC signal. The SYNC signal should be derived from the mains line. The acquisition will trig-
ger on a falling edge of this signal. To enable synchronization for a specific acquisition type, the
user must write a one to the SYNC bit in the appropriate Configuration Register 1 (MGCFG1,
ATCFG1, TGACFG1, or TGBCFG1).
For QMatrix acquisition, all X lines must be sampled at a specific phase of the noise signal for
the synchronization to be effective. This can be accomplished by the synchronization timer,
which is enabled by writing a non-zero value to the SYNCTIM field in the MGCFG2 register. This
ensures that the start of the acquisition of each X line is spaced at regular intervals, defined by
the SYNCTIM field.
By default, the CAT pins are driven with normal I/O drive properties. Some of the CSA and CSB
pins can optionally drive with a 1k output resistance for improved EMC. The pins that have this
capability are listed in the Module Configuration section.
The device integrates a discharge current source, which can be used to discharge the sampling
capacitors during the QMatrix measurement phase. The discharge current source is enabled by
writing the EN bits in the Discharge Current Source (DICS) register to one. This enables an
internal reference voltage, which can be the internal 1.1V band gap voltage or VDDIO/3, as
selected by the INTVREFSEL bit in the DICS register. If the DICS.INTREFSEL bit is one, the ref-
erence voltage is applied across an internal resistor. Otherwise the voltage is applied to the DIS
pin, and an external resistor must be connected between DIS and ground. This allows the dis-
charge current to be programmed between 2 and 20µA.
The reference current is mirrored to each Y-pin if the corresponding bit is written to one in the
DICS.SOURCES field.
The reference current can be fine-tuned by writing the trim value to the DICS.TRIM field, allow-
ing the user to compensate e.g. for temperature gradients in the resistance value.
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