WM9705_06 WOLFSON [Wolfson Microelectronics plc], WM9705_06 Datasheet - Page 44

• Manufacturer Part Number: WM9705_06
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

WM9705
w
Screen Switch
/ Input Mux
ADC MODE
EAPD/BUSY
PENDATA
mode
SDOUT
POLLING METHOD
The polling method relies on the controller to instruct every operation, i.e. to send an instruction
requesting every individual conversion specifically. A polled conversion is requested by writing a 1
to POLL bit 15 in register 76h, along with the address of the channel to be converted.
The channel to convert is identified by a 3-bit tag word ADR[2-0] written to the Pen control register
76h. This tag has the same value as the value read back with the conversion result, thus
identifying which channel the result is for, see Table 24.
conversion will take place and POLL will be reset.
If the channel to convert is an X or Y pen channel, then the appropriate screen driver switch
configuration is selected first, the screen allowed to settle for a time (selected by programming the
value into the DELAY register, DEL[3-0] in register 76h) and then the screen sample taken and
the conversion made. Figures A2 and A3 show the switch configurations for X and Y plate
conversions. Once the conversion is complete, the result is written into the results register 7Ah
where it is available for readback.
Figure 21 Control of ADC conversions : Polling Method
CO-ORDINATE METHOD
Setting bit COO in register 76h puts the device into Co-ordinate conversion mode.
Co-ordinate method of conversion instructs a sequence of conversions necessary to perform a
pen co-ordinate determination. Most basically this requires an X and a Y conversion but may also
include a pressure measurement. Writing to the POLL bit with COO bit in register 76h set
initiates a set of co-ordinate conversions, the results of which are returned to the controller as
soon as they are available.
If pressure conversion, or an auxiliary conversion are also required as part of the sequence, this is
instructed by writing the appropriate address into the ADR [2-0] bits of register 76h. (X and Y
addresses do not need to be set in this case, as they are implied by the choice of co-ordinate
method of operation). DEL[3-0] delays are applied as for polled operation to all conversions.
Subsequent POLL operations will then return both X and Y conversion results, plus the auxiliary
or pressure conversion result indicated by the value set in ADR[2-0].
Once a conversion is complete, the result is written into the results register 7Ah where it is
available for readback.
POLL
SYNC
Pen Detect or Off
Write to 0x76 with 0x8810
Single coordinate conversion with ADR = 000 (X and Y only) with delay set to 1 (2 frames)
X
delay = 2 frames
ADR = 001 - X measurement
DELAY
X
CONVERT
external signals
internal signals
delay = 2 frames
ADR = 010 - Y measurement
X measurement data
DELAY
If ADD[2-0] is set to 0 then no
PD Rev 4.4 August 2006
CONVERT
Production Data
Y measurement data
Pen Detect or Off
X
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