CAT5221WI-25 Datasheet, PDF (7/16 Pages) ON Semiconductor – Dual Digitally Programmable Potentiometer with 64 Taps and I2C Interface

WRITE OPERATION
In the Write mode, the Master device sends the
START condition and the slave address information to
the Slave device. After the Slave generates an
acknowledge, the Master sends the instruction byte
that defines the requested operation of CAT5221. The
instruction byte consist of a four-bit opcode followed
by two register selection bits and two pot selection
bits. After receiving another acknowledge from the
Slave, the Master device transmits the data to be
written into the selected register. The CAT5221
acknowledges once more and the Master generates
the STOP condition, at which time if a nonvolatile data
register is being selected, the device begins an
internal programming cycle to non-volatile memory.
While this internal cycle is in progress, the device will
not respond to any request from the Master device.
CAT5221
Acknowledge Polling
The disabling of the inputs can be used to take
advantage of the typical write cycle time. Once the
stop condition is issued to indicate the end of the
host's write operation, the CAT5221 initiates the
internal write cycle. ACK polling can be initiated
immediately. This involves issuing the start condition
followed by the slave address. If the CAT5221 is still
busy with the write operation, no ACK will be returned.
If the CAT5221 has completed the write operation, an
ACK will be returned and the host can then proceed
with the next instruction operation.
Figure 5. Slave Address Bits
CAT5221 0 1 0 1 A3 A2 A1 A0
* A0, A1, A2 and A3 correspond to pin A0, A1, A2 and A3 of the device.
** A0, A1, A2 and A3 must compare to its corresponding hard wired input pins.
Figure 6. Write Timing
S
T ^{SLAVE/DPP INSTRUCTION}
S
BUS ACTIVITY: ^{A ADDRESS}
BYTE
T
MASTER ^R
T
Fixed
Variable
DR WCR DATA _{op code}
Pot/WCR Data Register
Address Address
O
P
SDA LINE S
P
A
A
A
C
C
C
K
K
K
© 2008 SCILLC. All rights reserved.
7
Characteristics subject to change without notice
Doc. No. MD-2113 Rev. L