Datasheet

MCP3421
DS22003E-page 18 © 2009 Microchip Technology Inc.
FIGURE 5-1: MCP3421 Address Byte.
5.3.2 WRITING A CONFIGURATION BYTE
TO THE DEVICE
When the Master sends an address byte with the R/W
bit low (R/W = 0), the MCP3421 expects one
configuration byte following the address. Any byte sent
after this second byte will be ignored. The user can
change the operating mode of the device by writing the
configuration register bits.
If the device receives a write command with a new
configuration setting, the device immediately begins a
new conversion and updates the conversion data.
FIGURE 5-2: Timing Diagram For Writing To The MCP3421.
Start bit
Read/Write
bit
Address Byte
R/W ACK
1
1
0
1
X
X
X
Device Code Address Bits
(Note 1)
Address
Acknowledge bit
Address
Note 1: Specified by the customer and programmed at
the factory. If not specified by the customer,
programmed to ‘
000’.
9
1
9
1
Stop Bit by
11
0
1A2A1
A0
R/W
ACK by
MCP3421
RDY
C1 C0
O
/C
S1 S0 G1 G0
1st Byte:
2nd Byte:
Master
ACK by
MCP3421
MCP3421 Address Byte
Configuration Byte
Start Bit by
Master
with Write command
Note: – Stop bit can be issued any time during writing.
– MCP3421 device code is 1101.
– Address Bits A2- A0 = 000 are programmed at factory unless customer requests different codes.
SCL
SDA