MAX1233_05 Datasheet, PDF (18/45 Pages) Maxim Integrated Products – ±15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller

±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
PENIRQ returns high only after a touch-screen scan is
completed. PENIRQ does not go low again until one of
the touch-screen data registers is read. Figures 8a and
8b show the timing diagrams for the PENIRQ pin.
Keypad Interrupt Request (KEYIRQ)
The KEYIRQ output can be used to alert the host con-
troller of a key press. The KEYIRQ output is normally
high and goes low after a key press is detected.
KEYIRQ returns high only after a key-press scan is
completed. KEYIRQ does not go low again until one of
the key-press data registers is read. Figures 9a and 9b
show the timing diagrams for the KEYIRQ pin.
Busy Indicator (BUSY)
BUSY informs the host processor that a scan is in
progress. BUSY is normally high and goes low and
stays low during each functional operation. The host
controller should wait until BUSY is high again before
using the serial interface.
Digital Interface
The MAX1233/MAX1234 interface to the host controller
through a standard 3-wire serial interface at up to
10MHz. DIN and CS are the digital inputs to the
MAX1233/MAX1234. DOUT is the serial data output.
Data is clocked out at the SCLK falling edge and is high
impedance when CS is high. PENIRQ and KEYIRQ com-
municate interrupts from the touch-screen and keypad
controllers to the host processor when a screen touch or
a key press is detected. BUSY informs the host proces-
sor that a scan is in progress. In addition to these digital
I/Os, the row and column pins of the keypad controller
can be programmed as GPIO pins.
Communications Protocol
The MAX1233/MAX1234 are controlled by reading from
and writing to registers through the 3-wire serial inter-
face. These registers are addressed through a 16-bit
command that is sent prior to the data. The command
is shown in Table 2.
The first 16 bits after the falling edge of CS contain the
command word. The command word begins with an
R/W bit, which specifies the direction of data flow on
the serial bus. Bits 14 through 7 are reserved for future
use. Bit 6 specifies the page of memory in which the
desired register is located. The last 6 bits specify the
address of the desired register. The next 16 bits of data
R_
KEYIRQ
BUSY
CS
DATA
READ
DOUT
TOUCH-
SCREEN
DATA
Figure 9a. Timing Diagram for Key-Press-Initiated Debounce
Scan
R_
KEYIRQ
BUSY
CS
DATA
READ
DIN
DOUT
TOUCH-
SCREEN
DATA
Figure 9b. Timing Diagram for Host-Initiated Keypad
Debounce Scan
are read from or written to the address specified in the
command word. After 32 clock cycles, the interface
automatically increments its address pointer and con-
tinues reading or writing until the rising edge of CS, or
until it reaches the end of the page.
Table 2. Command Word Format
BIT15 _{BIT14 BIT13 BIT12 BIT11 BIT10}
MSB
R/W RES RES RES RES RES
BIT9
RES
BIT8
RES
BIT7
RES
BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 ^BIT0
LSB
PAGE ADD5 ADD4 ADD3 ADD2 ADD1 ADD0
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