Datasheet

MCP40D17/18/19
DS22152B-page 36 © 2009 Microchip Technology Inc.
5.2.9 I
2
C COMMAND PROTOCOL
The MCP40D17/18/19 is a slave I
2
C device which
supports 7-bit slave addressing. The slave address
contains seven fixed bits. Figure 5-9 shows the control
byte format.
5.2.9.1 Control Byte (Slave Address)
The Control Byte is always preceded by a START
condition. The Control Byte contains the slave address
consisting of seven fixed bits and the R/W bit. Figure 5-
9 shows the control byte format and Table 5-2 shows
the I
2
C address for the devices.
All devices are offered with the I
2
C slave address of
“0101110”, while the MCP40D18 also offers a second
standard I
2
C slave address of “0111110”.
FIGURE 5-9: Slave Address Bits in the
I
2
C Control Byte (Slave Address = “0101110”).
TABLE 5-2: DEVICE I
2
C ADDRESS
5.2.9.2 Hardware Address Pins
The MCP40D17/MCP40D18/MCP40D19 does not
support hardware address bits.
5.2.10 GENERAL CALL
The General Call is a method that the Master device
can communicate with all other Slave devices.
The MCP40D17/18/19 devices do not respond to
General Call address and commands, and therefore
the communications are Not Acknowledged.
FIGURE 5-10: General Call Formats.
SA6A5A4A3A2A1A0R/W
A/A
Start
bit
Slave Address
R/W bit
A bit (controlled by slave device)
R/W = 0 = write
R/W = 1 = read
A = 0 = Slave Device Acknowledges byte
A = 1 = Slave Device does not Acknowledge byte
“0” “1” “0” “1” “1” “1” “0”
Device I
2
C Address Comment
MCP40D17 ‘0101110’
MCP40D18
‘0101110’ MCP40D18-xxxE/LT
‘0111110’ MCP40D18-xxxAE/LT
MCP40D19 ‘0101110’
0000S 0000 XXX X XA XX0A P
General Call Address
Second Byte
“7-bit Command”
Reserved 7-bit Commands (By I
2
C Specification - Philips # 9398 393 40011, Ver. 2.1 January 2000)
“0000 011”b - Reset and write programmable part of slave address by hardware
“0000 010”b - Write programmable part of slave address by hardware
“0000 000”b - NOT Allowed
The Following is a “Hardware General Call” Format
0000S 0000 XXXXXA XX1A
General Call Address
Second Byte
“7-bit Command”
XXXXX XXXAP
n occurrences of (Data + A / A)
This indicates a “Hardware General Call”
MCP40D17/18/19 will ignore this byte and
all following bytes (and A), until a Stop bit
(P) is encountered.