TCS3404, TCS3414

DIGITAL COLOR SENSORS

TAOS137A − APRIL 2011

10

r

r

Copyright

E 2011, TAOS Inc.

The LUMENOLOGY

r Company

www.taosinc.com

Each Send and Write protocol is, essentially, a series of bytes. A byte sent to the TCS3404/14 with the most

significant bit (MSB) equal to 1 will be interpreted as a COMMAND byte. The lower four bits of the COMMAND

byte form the register select address (see Table 1), which is used to select the destination for the subsequent

byte(s) received. The TCS3404/14 responds to any Receive Byte requests with the contents of the register

specified by the stored register select address.

The TCS3404/14 implements the following protocols of the SMB 2.0 specification:

When an SMBus Block Write or Block Read is initiated (see description of COMMAND Register), the byte

following the COMMAND byte is ignored but is a requirement of the SMBus specification. This field contains

the byte count (i.e. the number of bytes to be transferred). The TCS3404 (SMBus) device ignores this field and

extracts this information by counting the actual number of bytes transferred before the Stop condition is

detected.

until a NACK is sent by the Master.

The data formats supported by the TCS3404 and TCS3414 devices are:

−

The transfer direction in this case is not changed.

−

At the moment of the first acknowledgment (provided by the slave receiver) the master transmitter

becomes a master receiver and the slave receiver becomes a slave transmitter.

−

During a change of direction within a transfer, the master repeats both a START condition and the slave

address but with the R/W bit reversed. In this case, the master receiver terminates the transfer by

generating a NACK on the last byte of the transfer and a STOP condition.

For

a

complete

description

of

SMBus

protocols,

please

review

the

SMBus

Specification

at

specification at http://www.i2c−bus.org/references/.