MCC iPort/LAN 2, Руководство пользователя

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3.3 Connecting to a Low-Voltage Target System
If you are connecting the I
2
C adapter to a low-voltage (<5v) target system, you
should follow these steps BEFORE applying power:
• Using the adapter MODE slide switch, put the adapter is Sense Mode.
• If you target system does NOT supply I
2
C Bus pull-ups, use the adapter
PULLUPS slide switch to enable the adapter’s internal 1.8K ohm pull-ups.
• Connect the I
2
C conV wire to the target system I
2
C Bus power. The I
2
C
adapter will be powered from its own +5V power supply, and adapters pull-ups,
if enabled, and Voltage Sense circuit will be powered by the target system’s low-
voltage power supply.
3.4 Connecting to an SMBus Target System
If you are connecting the I
2
C adapter to a SMBus target system, you should follow
these steps BEFORE applying power:
• Shut off the I
2
C adapter’s internal pull-ups (See Pull-up Resistor section).
• Use external SMBus rated (appoximately15k ohms) pull-up resistors. These
pull-ups may already be present in the target system.
• Visit our I
2
C versus SMBus FAQ page (www.mcc-us.com/I2CSMBusFAQ.htm).
• See the SMBus Specification for additional details.
Special Note for SMBus Users : MCC’s I
2
C adapters are designed to be I
2
C Bus
compatible, not SMBus compatible. Some features of the SMBus protocol not
supported include time-outs, device reset, and Packet Error Check byte processing.
The non-supported SMBus features may, or may not, permit the use of the I
2
C
adapter in your SMBus application. Consult the MCC FAQ web page and SMBus
Specification for details.