Datasheet

DeviceAddress
0
Slave Address
0
1
0 0
AD
DR
R/W
Fixed
Programmable
0
ControlRegisterandCommandByte
B2 B1
B0B5
B4
B3
B7
B6
TCA6408A
SCPS192C–APRIL2009–REVISEDJULY2009............................................................................................................................................................. www.ti.com
InterfaceDefinition
BIT
BYTE
7(MSB)6543210(LSB)
I
2
CslaveaddressLHLLLLADDRR/W
I/OdatabusP7P6P5P4P3P2P1P0
TheaddressoftheTCA6408AisshowninFigure4.
Figure4.TCA6408AAddress
AddressReference
ADDRI
2
CBUSSLAVEADDRESS
L32(decimal),20(hexadecimal)
H33(decimal),21(hexadecimal)
Thelastbitoftheslaveaddressdefinestheoperation(readorwrite)tobeperformed.Ahigh(1)selectsaread
operation,whilealow(0)selectsawriteoperation.
Followingthesuccessfulacknowledgementoftheaddressbyte,thebusmastersendsacommandbyte,whichis
storedintheControlRegisterintheTCA6408A.Twobitsofthisdatabytestatetheoperation(readorwrite)and
theinternalregisters(Input,Output,PolarityInversion,orConfiguration)thatwillbeaffected.Thisregistercanbe
writtenorreadthroughtheI
2
Cbus.Thecommandbyteissentonlyduringawritetransmission.
Figure5.ControlRegisterBits
CommandByte
CONTROLREGISTERBITSCOMMAND
POWER-UP
BYTEREGISTERPROTOCOL
DEFAULT
B7B6B5B4B3B2B1B0
(HEX)
0000000000InputPortReadbytexxxxxxxx
0000000101OutputPortRead/writebyte11111111
0000001002PolarityInversionRead/writebyte00000000
0000001103ConfigurationRead/writebyte11111111
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