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Power Studies

JPower

JPower is a tool that measures the amount of current flowing in the SLAAC-1V board. The 'J' in JPower is derived from Jason Zimmerman who made the tool operational while working at Los Alamos National Labs during the summer of 2003.

SLAAC-1V C API
JPower measures the current from the SLAAC-1V ADC by means of the SLAAC-1V C API, and then stores the value as a 10-bit unsigned number in a register (register 0x6A). The value in the register is then multiplied by 4.8828125 (625 >> 8) to produce the value of the current in mA (rounded to the nearest mA).

The SLAAC-1V board ADC has three different channels from which to measure current. Channel 0 reports the 5 Volt current, Channel 1 reports the 2.5 Volt current and Channel 2 reports the 3.3 Volt current. The ADC can be sampled at a rate of up to 120 kHz divided by the number of channels being sampled.

Current Isolation
Since JPower reports current in the entire SLAAC-1V board, it is important to distinguish the current used by all external devices from the current in the FPGA device we wish to examine (PE1 in our case). In order to remove the current from all other devices we use the equation:

313 + FREQ + CLK * (3 + 3 * FREQ)

FREQ = clock frequency
CLK = {0, 1} -> 1 when the clock is running

NOTE: The above equation is used when the default SLAAC-1V PE0 is loaded in X0. If a design is loaded into PE0, the above equation will change and the SLAAC-1V board must be completely powered down before the default design will again be loaded into PE0.

JPower Tools
The programs used to record current measurments from the SLAAC-1V board are given below. The first file is a C++ program which uses the SLAAC-1V API to sample current. A needed makefile is also given with that program. Note that the makefile will need to be modified before it can be used. The second file is a Perl script which executes the C++ executable a given number of times at a number of different frequencies.

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