41
32142DS–06/2013
ATUC64/128/256L3/4U
Fix/Workaround
Configure the lower channel with RA = 0x1 and RC = 0x2 to produce a dummy clock cycle
for the upper channel. After the dummy cycle has been generated, indicated by the
SR.CPCS bit, reconfigure the RA and RC registers for the lower channel with the real
values.
6.3.10 ADCIFB
1. ADCIFB DMA transfer does not work with divided PBA clock
DMA requests from the ADCIFB will not be performed when the PBA clock is slower than
the HSB clock.
Fix/Workaround
Do not use divided PBA clock when the PDCA transfers from the ADCIFB.
6.3.11 CAT
1. CAT QMatrix sense capacitors discharged prematurely
At the end of a QMatrix burst charging sequence that uses different burst count values for
different Y lines, the Y lines may be incorrectly grounded for up to n-1 periods of the periph-
eral bus clock, where n is the ratio of the PB clock frequency to the GCLK_CAT frequency.
This results in premature loss of charge from the sense capacitors and thus increased vari-
ability of the acquired count values.
Fix/Workaround
Enable the 1kOhm drive resistors on all implemented QMatrix Y lines (CSA 1, 3, 5, 7, 9, 11,
13, and/or 15) by writing ones to the corresponding odd bits of the CSARES register.
2. Autonomous CAT acquisition must be longer than AST source clock period
When using the AST to trigger CAT autonomous touch acquisition in sleep modes where the
CAT bus clock is turned off, the CAT will start several acquisitions if the period of the AST
source clock is larger than one CAT acquisition. One AST clock period after the AST trigger,
the CAT clock will automatically stop and the CAT acquisition can be stopped prematurely,
ruining the result.
Fix/Workaround
Always ensure that the ATCFG1.max field is set so that the duration of the autonomous
touch acquisition is greater than one clock period of the AST source clock.
3. CAT consumes unnecessary power when disabled or when autonomous touch not
used
A CAT prescaler controlled by the ATCFG0.DIV field will be active even when the CAT mod-
ule is disabled or when the autonomous touch feature is not used, thereby causing
unnecessary power consumption.
Fix/Workaround
If the CAT module is not used, disable the CLK_CAT clock in the PM module. If the CAT
module is used but the autonomous touch feature is not used, the power consumption of the
CAT module may be reduced by writing 0xFFFF to the ATCFG0.DIV field.
4. CAT module does not terminate QTouch burst on detect
The CAT module does not terminate a QTouch burst when the detection voltage is
reached on the sense capacitor. This can cause the sense capacitor to be charged more
than necessary. Depending on the dielectric absorption characteristics of the capacitor, this
can lead to unstable measurements.
Fix/Workaround
Use the minimum possible value for the MAX field in the ATCFG1, TG0CFG1, and
TG1CFG1 registers.
