AR1000_16 Datasheet, PDF (16/61 Pages) Microchip Technology – AR1000 Series Resistive Touch Screen Controller

AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
6. Master receives eight data bits (MSb first)
presented on SDA by the AR1021, at eight
sequential master clock (SCL) cycles. The data
is latched out on SCL falling edges to ensure it
is valid during the subsequent SCL high time.
7. If data transfer is not complete, then:
- Master acknowledges (ACK) reception of the
eight data bits by presenting a low on SDA,
followed by a low-high-low on SCL.
- Go to step 5.
8. If data transfer is complete, then:
- Master acknowledges (ACK) reception of the
eight data bits and a completed data transfer
by presenting a high on SDA, followed by a
low-high-low on SCL.
9. Master presents a “Stop” bit to the AR1021 by
taking SCL low-high, followed by taking SDA
low-to-high.
4.5 Master Write Bit Timing
Master write is to send supported commands to the
AR1021.
• Address bits are latched into the AR1021 on the
rising edges of SCL.
• Data bits are latched into the AR1021 on the
rising edges of SCL.
• ACK is presented by AR1021 on the ninth clock.
• The master must monitor the SCL pin prior to
asserting another clock pulse, as the AR1021
may be holding off the master by stretching the
clock.
FIGURE 4-2:
I²C MASTER WRITE BIT TIMING DIAGRAM
Steps
1. SCL and SDA lines are Idle high.
2. Master presents “Start” bit to the AR1021 by
taking SDA high-to-low, followed by taking SCL
high-to-low.
3. Master presents 7-bit Address, followed by a
R/W = 0 (Write mode) bit to the AR1021 on
SDA, at the rising edge of eight master clock
(SCL) cycles.
4. AR1021 compares the received address to its
device ID. If they match, the AR1021
acknowledges (ACK) the master sent address
by presenting a low on SDA, followed by a
low-high-low on SCL.
5. Master monitors SCL, as the AR1021 may be
“clock stretching”, holding SCL low to indicate
the master should wait.
6. Master presents eight data bits (MSb first) to the
AR1021 on SDA, at the rising edge of eight
master clock (SCL) cycles.
7. AR1021 acknowledges (ACK) receipt of the
eight data bits by presenting a low on SDA,
followed by a low-high-low on SCL.
8. If data transfer is not complete, then go to step 5.
9. Master presents a “Stop” bit to the AR1021 by
taking SCL low-high, followed by taking SDA
low-to-high.
4.6 Clock Stretching
The master normally controls the clock line SCL. Clock
stretching is when the slave device holds the SCL line
low, indicating to the master that it is not ready to
continue the communications.
During communications, the AR1021 may hold off the
master by stretching the clock with a low on SCL.
The master must monitor the slave SCL pin to ensure
the AR1021 is not holding it low, prior to asserting
another clock pulse for transmitting or receiving.
4.7 AR1020 Write Conditions
The AR1020 part does not implement clock stretching
on write conditions.
A 50 us delay is needed before the Stop bit, when
clocking a command to the AR1020.
DS40001393C-page 16
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