WM9705_06 WOLFSON [Wolfson Microelectronics plc], WM9705_06 Datasheet - Page 42

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

WM9705
READBACK OF PEN DIGITISER RESULTS
w
PRP[1:0]
RPR
PDEN
PINV
BSEN
BINV
WAIT
PIL
PHIZ
MSK[1:0]
PDD[3:0]
PNDN
ADR[2:0]
D[11:0]
BIT
BIT
15:14
13
12
11
10
9
8
7
6
5:4
3:0
15
14:12
11:0
LOCATION
LOCATION
INDEX 78H – DIGITISER CONTROL WORD 2 – READ/WRITE REGISTER
INDEX 7AH – DIGITISER DATA WORD OUTPUT – READ REGISTER ONLY
Readback
measurements, or auxiliary conversion, is via the AC link interface.
Readback may be performed either by reading from the read only register 7Ah via the AC link, or
by enabling SLOT mode (by writing SLEN = 1 in register 76h) where results are placed into the
AC link data slots by WM9705, and sent back to the controller.
The readback word contains the 12 bit data in the lsb locations, plus a 3 bit header in the next 3
bit locations, whose value corresponds to the channel that the data was converted from. Other
bits are padded with zero values. Channel addressing is the same as the address requested for
the conversion, as follows:
Pen digitiser power down bit control bits:
Enables PR4 reset on pen down wake up
BUSY flag enable. Outputs converter BUSY signal on pin 47. ‘1’ = converter busy, goes
WAIT bit; setting this bit causes conversion operations to halt when a result is about to
Sets PHONE and PCBEEP inputs to be High impedance by disconnecting them from
Selects what effect MASK input has:
Pen detect comparator threshold
00 – Pen digitiser powered down, pen detect disabled, no wakeup on pen down (default)
01 – Pen digitiser powered off, pen detect enabled, wakeup on pen down enabled
10 – Pen digitiser powered off, pen detect enabled, no wakeup on pen down
11 – Pen digitiser powered up
causes conversions and screen drives to stop when pen is not down
Inverts sense of PENDET output: Default ‘0’ causes PEN = ‘down’ to give a ‘1’ output
low at end of conversion to indicate result available
Invert sense of BUSY flag output
be written to the data register 7Ah, if the last stored result has not yet been read.
Conversions commence again once the result has been read
Pressure current select (‘0’=200uA, ‘1’=400uA)
mixer via an internal switch. Setting bit low opens the switch. Setting bit high closes
the switch. Default setting is low.
00 = MASK pin ignored
01 = Mask pin is static; ‘hi’ halts conversions
10 = Mask pin is edge sensitive; rising or falling edge delays conversions by DEL [3-0]
11 = Mask pin becomes a synchronise input; conversions happen after edge
0 to Vmid in 15 steps; 0h = use zero power comparator with Vmid threshold
1 = Vmid/15 threshold
15 = Vmid threshold
Indicates whether Pen is Down; ‘1’ = ‘Down’
Conversion Address; Indicates which channel the following result is for
ADC output result
of
conversion
results
from
either pen
FUNCTION
FUNCTION
co-ordinate
conversions,
PD Rev 4.4 August 2006
Production Data
pressure
42