LMH0303 Datasheet, PDF (11/27 Pages) National Semiconductor (TI) – 3 Gbps HD/SD SDI Cable Driver with Cable Detect

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Feature Description (continued)
Host
(for example,
FPGA)
GPO
SCL
SDA
LMH0303
#1
RSTI RSTO
LMH0303
#2
RSTI RSTO
LMH0303
SNLS285H – APRIL 2008 – REVISED MAY 2016
3.3V
LMH0303
#N
RSTI RSTO
Figure 4. SMBus Configuration for Multiple LMH0303 Cable Drivers
The RSTI pin of the first device is controlled by the system with a GPO pin from the host. The first LMH0303
RSTO pin is then daisy chained to the next device's RSTI pin. That device’s RSTO pin is connected to the next
device and so on.
The procedure at initialization is to:
1. Hold the host GPO pin Low in RESET, to the first device. RSTO output default is also Low which holds the
next device in RESET in the chain.
2. Raise the host GPO signal to LMH0303 #1 RSTI input pin.
3. Write to Address 0x2E Register 0 with the new address value (for example 0x2C).
4. Upon writing Register 0 in LMH0303 #1, its RSTO signal will switch High. Its new address is 0x2C, and the
next LMH0303 in the chain will now respond to the default address of 0x2E.
5. The process is repeated until all LMH0303 devices have a unique address loaded.
6. Direct SMBus writes and reads may now take place between the host and any addressed device.
The 7-bit address field allows for 128 unique addresses. The above procedure allows for the reprogramming of
the LMH0303 devices such that multiple devices may share the two-wire SMBus. Make sure all devices on the
bus have unique device IDs.
If power is toggled to the system, the SMBus address routine needs to be repeated.
7.4 Device Functional Modes
The LMH0303 features can be controlled through the pin or SMBus interface. SMBus Interface describes
detailed operation using SMBus interface.
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