WM9713L_06 WOLFSON [Wolfson Microelectronics plc], WM9713L_06 Datasheet - Page 63

• Manufacturer Part Number: WM9713L_06
• Description: AC 97 Audio + Touchpanel CODEC
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

Pre-Production
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INITIATION OF MEASUREMENTS
The WM9713L touchpanel interface supports both polling routines and DMA (direct memory access)
to control the flow of data from the touchpanel ADC to the host CPU.
In a polling routine, the CPU starts each measurement individually by writing to the POLL bit (register
74h, bit 9). This bit automatically resets itself when the measurement is completed.
Table 48 Touchpanel Digitiser Control (Initiation of Measurements)
In continuous mode (CTC = 1), the WM9713L autonomously initiates measurements (or sets of
measurements) at the rate set by CR, and supplies the measured data to the CPU on one of the
unused AC’97 time slots. DMA-enabled CPUs can write the data directly into a FIFO without any
intervention by the CPU core. This reduces CPU loading and speeds up the execution of user
programs in handheld systems.
Note that the measurement frequency in continuous mode is also affected by the DEL bits (see
“Touchpanel Settling Time”). The faster rates achieved when DEL = 1111 may be useful when the
ADC is used for auxiliary measurements.
74h
76h
78h
REGISTER
ADDRESS
9
8
9:8
11
10
BIT
POLL
CTC
CR
PDEN
PDPOL
LABEL
0
0
00
0
0
DEFAULT
Writing “1” initiates a measurement.
(when CTC is not set)
0: Polling mode
1: Continuous mode (for DMA)
Continuous mode rate (DEL C 1111)
00: 93.75 Hz (every 512 AC-Link frames)
01: 120 Hz (every 400 AC-Link frames)
10: 153.75 Hz (every 312 AC-Link frames)
11: 187.5Hz (every 256 AC-Link frames)
Continuous mode “fast rate” (DEL = 1111)
00: 8 kHz (every six AC-Link frames)
01: 12 kHz (every four AC-Link frames)
10: 24 kHz (every other AC-Link frame)
11: 48 kHz (every AC-Link frame)
NOTE: PENDIV bits in 44h [5:3] should be
set to 111 in 48kHz mode to ensure that
samples occur synchronously on the AC97
data channel
0: measure regardless of pen status
1: measure only when pen is down (when
CTC=0 and POLL=1, measurement is
delayed until pen-down; when CTC=1,
measurements are stopped on pen-up)
Sets polarity of PENDOWN flag:
0: non-inverted
1: inverted
DESCRIPTION
PP Rev 3.0 June 2006
WM9713L
63