MAX11803 Maxim Integrated Products, MAX11803 Datasheet - Page 32

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MAX11803

Manufacturer Part Number
MAX11803
Description
(MAX11800 - MAX11803) Ultra-Small Resistive Touch-Screen Controllers
Manufacturer
Maxim Integrated Products
Datasheet

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Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I
In autonomous conversion, the MAX11800/MAX11801
idle in TDM until a touch event occurs. The
MAX11800/MAX11801 begin an automated sequence
of measurements as defined by the configuration regis-
ter 0x08h.
The MAX11800/MAX11801 tag and log the data into the
FIFO once a measurement is taken. If a touch is still pre-
sent, the devices continue to idle in a LPM until the time,
as set by the configuration settings, expires. If no touch is
present at the expiration of the time set by the configura-
tion settings, the MAX11800/MAX11801 return to TDM to
await the next panel touch.
All measurement operations occur without any interven-
tion from the AP. The MAX11800/MAX11801 issue inter-
rupts when new data is available in the internal FIFO. The
device clears the interrupt when all data is read back.
The AP controls the readback of measurement data as
the data becomes available.
In autonomous conversion mode, the MAX11800/
MAX11801 automatically perform the combined com-
mand defined in the configuration register. The devices
continuously scan for panel touch events. Between
scans, the devices idle in a low-power mode according
to the present touch status.
The MAX11800/MAX11801 control the progression
through modes in clear-on-read mode. When the panel
touch is present, the MAX11800/MAX11801 return to a
Figure 15. Clear-on-Read Interrupt Operation
32
______________________________________________________________________________________
READBACK OPERATIONS ARE NOT SHOWN, INDICATED BY THE CLEARING OF THE AP-INITIATED INTERRUPT.
WAIT TIME BETWEEN TOUCH DETECTION AND INITIAL SCAN (t
SCAN DURATION (t
SCAN PERIOD (t
PANEL
TIRQ
SP
) IS CONTROLLED BY CONFIGURATION SETTINGS.
SD
) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS.
Clear-on-Read Interrupt Mode
TDM
Measurement Operations
t
INIT
DATA WRITTEN TO FIFO,
BEGINNING OF TOUCH EVENT
Combined Commands
INTERRUPT ISSUED
ACM SCAN
ETAG = 00
t
SD
2
C/SPI Interface
INIT
) IS SPECIFIED BY CONFIGURATION SETTINGS.
LPM
t
SP
INTERRUPT CLEARED
ACM SCAN
ETAG = 01
timed high-impedance LPM to minimize current, after
the data tagging operations are complete. The
MAX11800/MAX11801 idle in LPM until it is time to per-
form the next required scan, determined by the config-
uration register settings. When a touch is not present at
the end of a measurement, the device returns to idle in
TDM. In TDM, the device waits until a touch is detected
before initiating another set of autonomous measure-
ments.
The MAX11800/MAX11801 adopt a clear-on-interrupt
protocol (CORINT) when in autonomous conversion
mode. Between touch events, the devices idle in a low-
power TDM state. Upon detection of a touch, the
devices begin a sequence of automated measure-
ments. Each time a qualifying measurement is complet-
ed, the data for that measurement is written to the
internal FIFO. Qualifying measurements are measure-
ments that indicate the beginning and end of a touch
event, which meet aperture requirements (see the
Aperture Range Requirements section).
TIRQ issues an interrupt once a qualifying measure-
ment is completed and logged into the FIFO indicating
that new data is available for the AP to read back. The
MAX11800/MAX11801 continue to perform measure-
ments as required by the configuration settings.
Program the AP to service the interrupt immediately to
avoid a FIFO overflow and loss of data. TIRQ remains
asserted until all unread FIFO data has been read back
to the AP. The AP confirms that readback is complete
either by monitoring TIRQ or by monitoring the data
event tags embedded in the data for end-of-FIFO.
(ETAG = 11b). See Figure 15.
AP READBACK,
LPM
AP READBACK (FIFO STORES DATA)
INTERRUPT IS HELD PENDING
END OF TOUCH EVENT
ACM SCAN
ETAG = 10
BLOCK
SCAN
TDM

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