User Manual

8
I
2
C-bus Protocol
A Acknowledge (0)
N Not Acknowledged (1)
P Stop Condition
R Read (1)
S Start Condition
Sr Repeated Start Condition
W Write (0)
… Continuation of protocol
Master-to-Slave
Slave-to-Master
1 7 1 1 8 1 8 1 1
S Slave Address W A Register Address A Data A ... P
I
2
C-bus Write Protocol
1 7 1 1 8 1 1 7 1 1 8 1
S Slave Address W A Register Address A Sr Slave Address R A Data A
8 1 1
Data A ... P
1 7 1 1 8 1 8 1 1
S Slave Address R A Data A Data A ... P
I
2
C-bus Read Protocol
The I
2
C-bus standard provides for three types of bus trans-
action: read, write, and a combined protocol. During a
write operation, the rst byte written is a command byte
followed by data. In a combined protocol, the rst byte
written is the command byte followed by reading a series
of bytes. If a read command is issued, the register address
from the previous command will be used for data access.
Likewise, if the MSB of the command is not set, the device
will write a series of bytes at the address stored in the last
valid command with a register address. The command
byte contains either control information or a 5-bit register
address. The control commands can also be used to clear
interrupts.
The I
2
C-bus protocol was developed by Philips (now NXP).
For a complete description of the I
2
C-bus protocol, please
review the NXP I
2
C-bus design specication at http://
www.i2c−bus.org/references/.
I
2
C-bus Protocol
Interface and control are accomplished through an I
2
C-bus
serial compatible interface (standard or fast mode) to a set
of registers that provide access to device control functions
and output data. The devices support the 7-bit I
2
C-bus ad-
dressing protocol.
The device supports a single slave address of 0×39 Hex
using 7-bit addressing protocol. (Contact factory for other
addressing options.)
Figure 5b. Normalized LED Angular Emitting ProleFigure 5a. Normalized PD Responsitivity vs. Angular Displacement
I
2
C-bus Read Protocol - Combined Format
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
-50 -40 -30 -20 -10 0 10 20 30 40 50
Normalized Responsitivity
Angle (Deg)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60
Normalized Radiant Intensity
Angle (Deg)
Half-power point
Half-power
point