TCA8418E Datasheet, PDF (22/35 Pages) Texas Instruments – I2C CONTROLLED KEYPAD SCAN IC WITH INTEGRATED ESD PROTECTION

TCA8418E
SCPS222B – MAY 2010 – REVISED SEPTEMBER 2010
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Reads
The bus master first must send the TCA8418E address with the LSB set to a logic 0. The command byte is sent
after the address and determines which register is accessed. After a restart, the device address is sent again
but, this time, the LSB is set to a logic 1. Data from the register defined by the command byte then is sent by the
TCA8418E (see Figure 11 and Figure 12). Data is clocked into the register on the rising edge of the ACK clock
pulse.
Slave Address
Acknowledge
From Slave
Acknowledge
From Slave
Slave Address
Acknowledge
From Slave
Data From Lower
or Upper Byte _Acknowledge
of Register _{From Master}
S
0
1
0
0
0
0
AD
DR
0
A
R/W
Command Byte
A
S
0
1
0
0
0
0
AD
DR
1
A
At this moment, master transmitter
R/W
becomes master receiver, and
slave receiver becomes slave transmitter.
Data
A
First Byte
Data From Upper
or Lower Byte No Acknowledge
of Register
From Master
MS
Data
LS NA P
Figure 11. Read From Register
Last Byte
SCL
123456789
Data from Port
Data from Port
SDA
S
0
1
0
0
0
0
AD
DR
1
A
Data 1 1 A
Data 4
Read From
Port
Data Into
Port
R/W Acknowledge
From Slave
Acknowledge
From Master
AP
Acknowledge
From Master
INT
t_iv
t_ir
Figure 12. Read From Input Port Register
22
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