MGC3140 datasheet(32/49 Pages) MICROCHIP

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Figure 7-3. I2C Master Write Bit Timing Diagram

Address

R/W

ACK

Data

Address Bits Latched in

Data Bits Valid Out

SCL may be stretched

Start Bit

Stop Bit

SDA

SCL

•

Address bits are latched into the MGC3140 on the rising edges of SCL.

•

Data bits are latched into the MGC3140 on the rising edges of SCL.

•

ACK bit:

–

MGC3140 presents the ACK bit on the ninth clock for address acknowledgment

–

I2C master presents the ACK bit on the ninth clock for data acknowledgment

•

The master must monitor the SCL pin prior to asserting another clock pulse, as the MGC3140 may

be holding off the master by stretching the clock.

I2C Communication Steps

SCL and SDA lines are Idle high.

I2C master presents Start bit to the MGC3140 by taking SDA high-to-low, followed by taking SCL

high-to-low.

I2C master presents 7-bit address, followed by a R/W = 0 (Write mode) bit to the MGC3140 on

SDA, at the rising edge of eight master clock (SCL) cycles.

MGC3140 compares the received address to its Device ID. If they match, the MGC3140

acknowledges (ACK) the I2C master sent address by presenting a low on SDA, followed by a low-

high-low on SCL.

I2C master monitors SCL, as the MGC3140 may be clock stretching, holding SCL low to indicate

the I2C master should wait.

I2C master presents eight data bits (MSB first) to the MGC3140 on SDA, at the rising edge of eight

master clock (SCL) cycles.

MGC3140 acknowledges (ACK) receipt of the eight data bits by presenting a low on SDA, followed

by a low-high-low on SCL.

If data transfer is not complete, then go to Step 5.

Master presents a Stop bit to the MGC3140 by taking SCL low-high, followed by taking SDA low-to-

high.

Important: The Stop condition after an I2C data transmission is generated by the host

controller (I2C master) after the data transfer is completed. Thus, it is recommended to verify the

number of bytes to be read in the message header (Size field).

7.3

Gesture Port

The MGC3140 provides five output pins which can be used to indicate gesture events. These pins are

controlled by GestIC Library to signal that an event occurred. The host does not need to monitor the I2C

bus to get GestIC Library events, but only has to monitor the Gesture Port pins. This feature can be used

in parallel to I2C communication.

MGC3140

Interface Description

DS40002037A-page 32

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