AMIS-30624 I2C Microstepping Motordriver
Data Sheet
2) If the microcontroller wants to receive information from motordriver_2:
• Microcontroller (master) addresses motordriver_2 (slave)
• Microcontroller (master-receiver) receives data from motordriver_2 (slave-transmitter)
• Microcontroller terminates the transfer
Even in this case the master generates the timing and terminates the transfer.
Generation of the signals on the I2C-bus is always the responsibility of the master device. It generates its own clock signal when
transferring data on the bus. Bus clock signals from a master can only be altered when they are stretched by a slow slave device
holding-down the clock line.
16.3 General Characteristics
+5 V
Rp
Rp
Serial Data Line
Serial Clock Line
SCK
SDA
SCL
SDA
2
1
Clock IN
Data IN
Clock IN
Data IN
Clock OUT
Data OUT
Clock OUT
Data OUT
AMIS-30624
MASTER
PC20060925.7
Figure 24: Connection of a Device to the I2C-bus
Both SDA and SCK are bi-directional lines connected to a positive supply voltage via a pull-up resistor (see Figure 24). When the bus is
free both lines are HIGH. The output stages of the devices connected to the bus must have an open drain to perform the wired-AND
function. Data on the I2C-bus can be transferred up to 400kbits/s in fast mode. The number of interfaces connected to the bus is
dependent on the maximum bus capacitance limit (See CB in Table 6) and the available number of addresses.
16.4 Bit Transfer
The levels for logic ‘0’ (LOW) and ‘1’ (HIGH) are not fixed in the I2C standard but dependent on the used VDD level. Using AMIS-30624,
the levels are specified in Table 5. One clock pulse is generated for each data bit transferred.
16.4.1. Data Validity
The data on the SDA line must be stable during the HIGH period of the clock. The HIGH or LOW state of the data line can only change
when the clock signal on the SCL line is LOW (See Figure 25).
SDA
SCK
Data line stable
-> Data valid
Change of
data allowed
PC20070217.2
Figure 25: Bit Transfer on the I2C-bus
AMI Semiconductor – Apr. 2007, Rev 3.1, M-20664-003
40
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