TCA8418 Datasheet, PDF (22/37 Pages) Texas Instruments – I2C CONTROLLED KEYPAD SCAN IC WITH INTEGRATED ESD PROTECTION

TCA8418
SCPS215 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com
SCL
12 3 456 7 8 9
Slave Address
Command Byte
Data to Port
SDA
S
0
1
0
00
0
AD
DR
0
A0
00
0
0
0
10
A
Data 1
Start Condition
Write to Port
R/W Acknowledge
From Slave
Acknowledge
From Slave
0.0 A P
Acknowledge
From Slave
Data Out
from Port
Figure 9. Write to Output Port Register
Data Valid
t_pv
SCL
1234 56789
Slave Address
Command Byte
Data to Register
SDA S
0
1
0
0
0
0
AD
DR
0
A
0
0
0
0
0
0
1
1
A
Data
AP
Start Condition
R/W Acknowledge
From Slave
Acknowledge
From Slave
Figure 10. Write to Configuration or Polarity Inversion Register
Acknowledge
From Slave
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
22
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