Datasheet
20 SERDESUB-21USB User’s Guide SNLU101 – April 2012
Evaluation of the Bi-directional Control Channel
This section describes how to perform I
2
C instructions between MCU/FPGA and a remote
peripheral device through the DS90UB904Q and DS90UB903Q pair configured in a
display type of application. Figure 4 shows the configuration of evaluation boards for I
2
C
communication. A MCU/FPGA controller with an I
2
C interface is required. Refer to the
DS90UB903Q/904Q datasheet for the definition of each register.
DS90UB904Q
Deserializer
SCL
SDA
PDB
RIN
+
-
ID[x]
PASS
LOCK
PCLK
VDDIO
MODE (M_S)
DS90UB903Q
Serializer
SCL
SDA
PDB
VDDIO
DOUT
+
-
ID[x]
PCLK
VDDIO
RES0
VDDIO
0xB0
BISTEN, RES0
GPU/FPGA
Host
SCL
SDA
VDDIO
MODE (M_S)
Timing Controller
µ
C
LCD
Display
1.8V 3.3V 1.8V 3.3V
(3.3V I/O)(3.3V I/O)
VDD18
VDDIO
VDD18
VDDIO
ROUT[20:0]
GPI0
GPI1
GPI2
GPI3
0xC0
0xA0
1.0k
1.0k
1.8V1.8V
00
10k 10k
DIN[20:0]
GPO0
GPO1
GPO2
GPO3
1.0k1.0k
DS90UB904Q
Deserializer
SCL
SDA
PDB
RIN
+
-
ID[x]
PASS
LOCK
PCLK
VDDIO
MODE (M_S)
DS90UB903Q
Serializer
SCL
SDA
PDB
VDDIO
DOUT
+
-
ID[x]
PCLK
VDDIO
RES0
VDDIO
0xB0
BISTEN, RES0
GPU/FPGA
Host
SCL
SDA
VDDIO
MODE (M_S)
Timing Controller
µ
C
LCD
Display
1.8V 3.3V 1.8V 3.3V
(3.3V I/O)(3.3V I/O)
VDD18
VDDIO
VDD18
VDDIO
ROUT[20:0]
GPI0
GPI1
GPI2
GPI3
0xC0
0xA0
1.0k
1.0k
1.8V1.8V
00
10k 10k
DIN[20:0]
GPO0
GPO1
GPO2
GPO3
1.0k1.0k
Figure 4. Example of DS90UB903Q/904Q in Display Application
Display Mode:
In Display mode, I
2
C transactions originate from the controller attached to the Serializer.
The I
2
C slave core in the Serializer will detect if a transaction targets (local) registers
within the Serializer or the (remote) registers within the Deserializer or a remote slave
connected to the I
2
C master interface of the Deserializer. Commands are sent over the
forward channel link to initiate the transactions. The Deserializer will receive the command
and generate an I
2
C transaction on its local I
2
C bus. At the same time, the Deserializer
will capture the response on the I
2
C bus and return the response as a command on the bi-
directional control channel. The Serializer parses the response and passes the appropriate
response to the Serializer I
2
C bus.