71M6403
Electronic Trip Unit
SEPTEMBER 2006
CE Program and Environment
CE Program
The CE program is supplied by TERIDIAN as a data image that can be merged with the MPU operational code for circuit breaker
applications. Typically, the CE program covers most applications and does not need to be modified. Proper operation of the CE
requires the following environment variables to be set as follows: FIR_LEN = 0, MUX_DIV = 0 and EQU = 101.
Formats
All CE words are 4 bytes. Unless specified otherwise, they are in 32-bit two’s complement (-1 = 0xFFFFFFFF). ‘Calibration’ para-
meters are defined in flash memory (or external EEPROM) and must be copied to CE memory by the MPU before enabling the
CE. ‘Internal’ variables are used in internal CE calculations. ‘Input’ variables allow the MPU to control the behavior of the CE
code. ‘Output’ variables are outputs of the CE calculations. The corresponding MPU address for the most significant byte is
given by 0x1000 + 4 x CE_address and 0x1003 + 4 x CE_address for the least significant byte.
Constants
Constants used in the CE Data Memory tables are:
ꢀ
ꢀ
Sampling frequency: FS = 32768Hz/13 = 2520.62Hz.
IMAX is the external rms current corresponding to 250mV pk at the inputs I0 through I5.
The system constant IMAX is used by the MPU to convert internal digital quantities (as used by the CE) to external, i.e. current
quantities. Their values are determined by the scaling of the current sensors used in an actual circuit breaker. The LSB values
used in this document relate digital quantities at the CE or MPU interface to external circuit breaker input quantities.
Environment
Before starting the CE using the CE_EN bit, the MPU has to establish the proper environment for the CE by implementing the
following steps:
•
•
•
•
•
Loading the image for the CE code into CE PRAM.
Loading the CE data into CE DRAM.
FIR_LEN = 0 (two cycles per conversion)
MUX_DIV = 0 (6 conversions per mux cycle)
EQU = 101
During operation, the MPU is in charge of controlling the multiplexer cycles. For example, by inserting an alternate multiplexer
sequence at regular intervals using MUX_ALT to enable temperature measurement. The polarity of CHOP must be altered for
each sample. It must also alternate for each alternate multiplexer reading.
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© 2006 TERIDIAN Semiconductor Corporation
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