Initialization/Application Information - Freescale Semiconductor MCF52277 Reference Manual

ASP_CR Field
Pen Sample FIFO
Data Format
No data is written
0 0
to the FIFO
0 1 U ,...,U
n
No data is written
1 0
to the FIFO
U ,...,U
n
1 1 U ,...,U
n
...
22.5

Initialization/Application Information

After reset, the ASP module is in power-down mode. Configure the module according to the application
requirements. Then, enable the module by clearing ASP_CR[MDIS]. The suggested configuration for
various typical applications is defined in this section.
22.5.1 Touchscreen Mode 00
Touchscreen mode 00 provides the most flexibility. All control of the bias switches and reference/input
muxes is dependent on ASP_SET. Starting the conversion is also fully decided by asserting ASPE. With
this flexibility, you can freely define your own operation sequence. Although TSE is set in this mode, you
can also use this mode to implement complex general-purpose ADC conversion sequences. Because of this
flexibility, it is the only mode not suitable for basic operation and requires the heaviest load on the
processor. Therefore, it is highly recommended not to use this mode, unless other modes cannot achieve
the required operation.
Figure 22-10 and Figure 22-11
MODE = 00 (AUTO, AZE, PENE, MIDLECNT, and RIDLECNT are not relevant to the operation).
Freescale Semiconductor
Table 22-12. General ADC Operating Modes (TSE=0)
When ASPE is cleared, there is no operation.
When ASPE is set, the ASP starts one round of conversion. For each active auxiliary
channel an ADC conversion is initiated. The process repeats until the last active auxiliary
channel is complete. Between each conversion, optional measurement idle time can be
1
inserted using ASP_TIM[MIDLECNT].
If no auxiliary channel is active (ASP_CR[APTN] = 0x00), there is no operation.
When ASPE is cleared, there is no operation.
When ASPE is set, the ASP starts continuous conversion on active auxiliary channels.
The measurement sequence is started from highest numbered active channel to lowest
numbered active channel. The same sequence repeats until ASPE is cleared. For each
,
1
active auxiliary channel an ADC conversion is initiated. Between each conversion, except
,
1
the round that wraps to the highest numbered auxiliary channel, 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].
If no auxiliary channel is active (ASP_CR[APTN] = 0x00), there is no operation.
illustrate a typical operation sequence when TSE = 1, CALA = 0,
MCF52277 Reference Manual, Rev. 1
Touchscreen Controller/Analog-to-Digital Converter
Notes
22-17