IC-PI datasheet(18/49 Pages) ICHAUS

18 / 49 page

preliminary

iC-PI PROGRAMMABLE 12-BIT

Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

Rev B1, Page 18/48

else

ucCRC = (ucCRC << 1 ) ;

ucDataStream = ucDataStream << 1 ;

}

I2C Slave Mode (ENSL = 1)

In this mode iC-PI behaves like an I2C slave with the

device ID 0x55 and the I2C interface permits iC-PI’s

internal registers to be read and written. An I2C start

condition (S) is indicated by a falling edge on SDA while

SCL remains high. This initiates the I2C sequence and

prevents other masters from driving the bus. Next, the

iC-PI device ID (0x55) must be written by the master

followed by the read/write mode bit (W). A low W bit

selects write mode and a high W bit selects read mode.

iC-PI acknowledges the valid device ID by pulling SDA

low while the master is not driving SDA (A).

The next 8 bits are the iC-PI address at which the data

is to be written. After the 8th bit, iC-PI again acknowl-

edges the received bits by pulling SDA low after a falling

edge on SCL. The third and following bytes contain the

data to be written. After a byte has been written, the

address is incremented so that multiple bytes can be

written sequentially. If the address is valid, the iC-PI

acknowledges the write command. After the last byte,

the master must release SCL so it is pulled high and

then also release SDA to generate a stop condition (P).

SCL

SDA

ADDRESS

6 5 4 3 2 1 0

1 0 1 0 1 0 1 W

DEVID

DATA

7 6 5 4 3 2 1 0

Figure 5: I2C write command in slave mode

For reading a register via I2C interface, the desired reg-

ister address must be sent to the iC-PI via an I2C write

command. After the address is acknowledged by iC-PI,

the master has to restart (R) the I2C sequence by plac-

ing a second start edge on SDA with SCL remaining

high. Next, the read command begins with the DEVICE

ID and the read/write mode bit (W) set to select read

mode (high). If the address is valid, the iC-PI acknowl-

edges the register read by pulling SDA low (A) and

then transmits the register contents of the specified ad-

dress. After a byte is read, the address is incremented

so that multiple bytes can be read sequentially. After

each byte, the master has to acknowledge that the byte

was received by pulling SDA low. Otherwise the iC-PI

goes into I2C idle mode. Figure 7 shows a read request

of position data at addresses 0x34 and 0x35, and the

latch event of the sensor data.

SCL

SDA

1 0 1 0 1 0 1 W

DEVID

ADDRESS

6 5 4 3 2 1 0

1 0 1 0 1 0 1 R

DEVID

DATA

7 6 5 4 3 2 1 0

Figure 6: I2C read command in slave mode

SCL

SDA

1 0 1 0 1 0 1 W

DEVID

ADDRESS

0 1 1 0 1 0 0

1 0 1 0 1 0 1 R

DEVID

DATA

7 6 5 4 3 2 1 0

REQUEST

DATA

7 6 5 4 3 2 1 0

Figure 7: I2C position data read command in slave mode

Device Configuration Using I2C Slave Mode

The registers 0x00 to 0x2E must be initialized with cor-

rect values before enabling iC-PI. This can be done

through the I2C slave interface if iC-PI is used without

an EEPROM or if the EEPROM content is invalid. Ini-

tially, RUN (bit 7 of address 0x02) must be set to zero,

then all registers must be configured. Finally, set RUN

to one without changing other bits of address 0x02 to

enable the device.

RUN

Addr. 0x02, bit 7

Code

Function

Device standby: Sin/D converter disabled and all

output drivers forced low (configuration changes

allowed, see Table 12)

Device enabled: Restart of Sin/D conversion, output

drivers active (configuration data must be valid)

Notes

RUN is evaluated only during I2C slave mode.

Writing changes the function.

Reading does not return the chip’s state.

Table 9: Device Enable

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