MAX11800_1010 Datasheet, PDF (32/59 Pages) Maxim Integrated Products – Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface

Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I²C/SPI Interface
Measurement Operations
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.
Combined Commands
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.
Clear-on-Read Interrupt Mode
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
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.
BEGINNING OF TOUCH EVENT
END OF TOUCH EVENT
PANEL
TOUCH
TIRQ
DATA WRITTEN TO FIFO,
INTERRUPT ISSUED
AP READBACK,
INTERRUPT IS HELD PENDING
INTERRUPT CLEARED _{AP READBACK (FIFO STORES DATA)}
SCAN
BLOCK
TDM
LPM
LPM
TDM
ACM SCAN
ACM SCAN
ACM SCAN
ETAG = 00
ETAG = 01
ETAG = 10
t_INIT
t_SD
t_SP
READBACK OPERATIONS ARE NOT SHOWN, INDICATED BY THE CLEARING OF THE AP-INITIATED INTERRUPT.
WAIT TIME BETWEEN TOUCH DETECTION AND INITIAL SCAN (t_INIT) IS SPECIFIED BY CONFIGURATION SETTINGS.
SCAN DURATION (t_SD) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS.
SCAN PERIOD (t_SP) IS CONTROLLED BY CONFIGURATION SETTINGS.
ACM = AUTONOMOUS CONVERSION MODE
Figure 15. Clear-on-Read Interrupt Operation—MAX11800/MAX11801
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