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PCHS/TPCHS SERIES Quick-Set PowerCassette®
INSTALLATION & OPERATING MANUAL
Manual No. tpchs-2
pchs-tpchs-man-rev2-1214.indd
APPENDIX 2
PowerCassette
®
: I²C SERIAL BUS INTERFACE
Status Indication of system critical power supply parameters
DESCRIPTION
The I²C interface that is incorporated into the PowerCassette includes facilities to monitor various operating
parameters within the unit and transmit these to a host computer on demand over an industry standard I²C
Serial bus.
Three forms of data are available. These allow the user to monitor the actual status of an individual unit,
manage system loading through measurement of the actual load on each output and also control inventory
through an inbuilt EEPROM containing specific data about each individual unit.
The implementation of I²C that has been utilized in PowerCassette is a subset of more complete implementations
such as IPMI. This data-sheet is intended as a supplement to the data sheet for the
PowerCassette
family
itself and should provide enough information for the system designer to make decisions on how to utilize
the available information within his overall system philosophy.
I²C DEVICES EMPLOYED
PCF8574
This device is an 8-bit digital register manufactured by
Philips.
PCF8591
This device is a Quad A/D converter manufactured by
Philips.
24C02
This device is a 256 byte EEPROM manufactured by
Atmel or ST
MAX6633
This is a 12-bit temperature measurement device
manufactured by Maxim.
For detailed information about the operation of these devices please consult the original manufacturers’
data-sheets.
ELECTRICAL INTERFACE
Addressing (GA0 and GA1)
Two external address lines are employed allowing up to
four PowerCassette modules to be addressed on a single
I²C bus.
Module addressing is achieved through hard-wiring the
address lines to 0V or the 5V auxiliary supply via a 100R
resistor on the system back-plane. In this way it is the
location or position of the module rather than any particular
module that is identified by an individual address.
Serial Clock (SCLK)
This line is clocked by the processor which controls the
I²C serial bus. It
should be tied to +5V via a pull-up resistor in the range
3k to 10k.
Serial Data (SDA)
This line is a bidirectional data line. It should be tied to
+5V via a pull-up resistor in the range 3k to 10k.
Interrupt
This line provides an interrupt to the processor in the event
of a change of status of the digital register.
BUS speed
The I²C interface as used in PowerCassette is designed to
run with a serial clock speed 100kHz.
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