Datasheet

AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
DS41393B-page 22 Preliminary  2009-2012 Microchip Technology Inc.
5.2 SPI Pin Voltage Level
Characteristics
5.3 Data Flow
SPI data is transferred by the host clocking the AR1021
controller’s Serial Clock (SCK) pin.
Each host driven clock cycle simultaneously shifts a bit
of data into and out from the AR1021 controller:
• Out from the AR1021 controller’s Serial Data Out
(SDO) line.
• Into the AR1021 controller’s Serial Data In (SDI)
line.
The data is shifted Most Significant bit (MSb) first.
If the host clocks data out from the AR1021 controller
when no valid data is available, then a byte value of
0x4d will be presented by the controller.
5.4 Touch Report Protocol
The AR1021 controller’s touch reporting is interrupt
driven:
• The AR1021 controller asserts the SIQ interrupt
pin high when it has a touch report ready.
• The host clocks out the bytes of the touch report
packet from the AR1021 controller.
• The AR1021 controller clears the SIQ interrupt pin
low, after the first byte of the touch report packet
has been clocked out by the host.
The communication protocol for the AR1021 controller
reporting touches to the host as shown below in
Figure 5-1.
FIGURE 5-1: SPI TOUCH REPORT PROTOCOL
TABLE 5-2: SPI PIN VOLTAGE CHARACTERISTICS
Operating Voltage: 2.5V ≤ VDD ≤ 5.25V
Function Pin Input Output
SCK SCL/SCK/TX V
SS ≤ VIL ≤ 0.2*VDD
0.8*VDD ≤ VIH ≤ VDD
—
SDI SDI/SDA/RX V
SS ≤ VIL ≤ 0.2*VDD
0.8*VDD ≤ VIH ≤ VDD
—
SDO SDO — VSS ≤ VOL
(1)
≤ (1.2V – 0.15*VDD)
(2)
(1.25*VDD – 2.25V)
(3)
≤ VOH
(1)
≤ VDD
SIQ SIQ — VSS ≤ VOL
(1)
≤ (1.2V – 0.15*VDD)
(2)
(1.25*VDD – 2.25V)
(3)
≤ VOH
(1)
≤ VDD
SS SS VSS ≤ VIL ≤ 0.2*VDD
0.8*VDD ≤ VIH ≤ VDD
Note 1: These parameters are characterized but not tested.
2: At 10 mA.
3: At -4 mA.