Touchscreen Controller/Analog-to-Digital Converter
MCF52277 Reference Manual, Rev. 1
22-16
Freescale Semiconductor
22.4.2
General ADC Function
When the block is configured as a general ADC (ASP_CR[TSE] = 0), the touchscreen bias network
completely switches off automatically.
describes the block’s operation.
10
0
x
1
U
n
,…,U
1
U
i
indicates the active auxiliary channel numbering from high to low. For example, if
the touchscreen controller is configured as a 4-wire interface, ADC_IN[7:4] is
available for ADC conversion by setting the corresponding bit in ASP_CR[APTN].
Between each conversion, optional measurement idle time may be inserted using
ASP_TIM[MIDLECNT]. After the X and Y conversions, no more conversions occur in
the current round and pen-up detection is active. AZE has no effect when only
general-purpose channels are converted. To start another round of conversion, the
ASPE must be first cleared and set again.
Touchscreen & Auxiliary Input Sample Mode
11
1
0
0
No data is written
to the FIFO
The touchscreen is parked in the pen-detection state.
11
1
0
1
X,Y,U
n
,…,U
1
,
X,Y,U
n
,…,U
1
,
…
After ASPE is set, the continuous conversion on touchscreen coordinates and active
auxiliary channels begins. Between each conversion except the round that wraps to
X coordinate conversion, optional measurement idle time can be inserted using
ASP_TIM[MIDLECNT]. At the end of each round of conversion, there is an option to
insert round idle time using ASP_TIM[RIDLECNT]. Between each round of
conversion, you may insert one pen-down detection phase after the round idle phase.
The pen detection circuit is active if ASP_SET[SW] is set.
11
1
1
0
No data is written
to the FIFO
The touchscreen is parked in the pen-detection state.
11
1
1
1
AZX, X, AZY, Y,
U
n
,…,U
1
AZX, X, AZY, Y,
U
n
,…,U
1
,
…
Similar to the operation when AZE is cleared. However, the auto-calibration of the 0
value measurements are made for the touchscreen before X/Y measurement. No
measurement idle phase is inserted between the auto-zero and the X/Y
measurement.
11
0
0
0
No data is written
to the FIFO
The touchscreen is parked in the pen-detection state.
11
0
0
1
X,Y,U
n
,…,U
1
After ASPE is set, one round of conversion of touchscreen coordinates and active
auxiliary channels begins. Between each conversion, optional measurement idle time
may be inserted using ASP_TIM[MIDLECNT]. After the X and Y conversions, no
more conversions occur in the current round and pen-up detection is active.
11
0
1
0
No data is written
to the FIFO
The touchscreen is parked in the pen-detection state.
11
0
1
1
AZX, X, AZY, Y,
U
n
,…,U
1
Similar to the operation when AZE is cleared. However, the auto-calibration of the 0
value measurements are made for the touchscreen before X/Y measurement. No
measurement idle phase is inserted between the auto-zero and the X/Y
measurement.
Table 22-11. Touchscreen Controller Operating Modes (TSE = 1) (continued)
ASP_CR Field
Pen Sample FIFO
Data Format
Notes
MODE
AU
T
O
AZE
ASPE
Summary of Contents for MCF52277
Page 22: ...MCF52277 Reference Manual Rev 1 Freescale Semiconductor xxii...
Page 32: ...MCF52277 Reference Manual Rev 0 xxxii Freescale Semiconductor...
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