PM9904BPD datasheet(4/22 Pages) SAMES

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PM9904BPD

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PM9904BPD EVALUATION SOFTWARE

Software for the SA9904AP module is supplied on one 3.5”

1.44MB floppy disk and is designed to communicate with the

SA9904AP module via the PC’s parallel port. The supplied

software is written for DOS. Additional Windows software will

be posted to the SAMES web site for downloading when

available. The source code, written in Turbo C, is also

included.

File description

The following files are included on the floppy disk:

9904mtr.c

This file contains the source for the functions that read the

SA9904 registers, store these values in integration registers,

check for any overflow and generate the corresponding

energy pulse for the PM9904BPD on-board LED’s. It makes

provision to measure unbalanced energy per phase or sum the

energy for each phase. The software does not make use of

timers and relies on counting the software loops to generate

reasonable delays for the LED outputs.

pc_spi.c

This file contains the source for all the SPI interface routines

which are used to communicate between the PM9904BPD

module and th e PC’s parallel port.

pc_lcd.c

This file contains the source for all the functions relating to the

SA8807 LCD driver IC, as well as other functions to switch on

the LCD display icons.

9904mtr.exe

This is the executable file.

Running the software

The program is executed by running the 9904mtr.exe file with

the following arguments:

9904mtr.exe 1 10

The first parameter specifies the LPT port address to use

where 1= 0x378 (LPT1) and 2 = 0x278 (LPT2).

The second parameter is a loop delay. Larger values will slow

down the SPI communication speed to the PM9904BPD

module.

Read Active Register

Subtract previous value

Add to active energy integrator

Generate pulse

If integrator > threshold

Subtract threshold from integrator

Load creep timer

Wait for next measurement cycle

Do other functions on the meter

Yes

Check and fix register value wrapping

Read Active Register

Subtract previous value

Add to active energy integrator

Generate pulse

If integrator > threshold

Subtract threshold from integrator

Load creep timer

Wait for next measurement cycle

Do other functions on the meter

Yes

Check and fix register value wrapping

Figure 4: Pulse flow diagram

Getting the SA9904 to generate pulses proportional

to the energy measured.

Figure 4 is a flow diagram showing how to generate pulses

proportional to energy measured by the SA9904A. The speed

of execution is not critical, although it will influence the

resolution of the pulses that is generated.

It is recommended that the flow diagram be implemented

together with a timer interrupt used for the creep timing. The

same flow diagram is applicable for the SA9604A, but reading

of the register values should be synchronized with changes in

bit D19 of its frequency register.

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Threshold and pulse rates

The active and reactive registers on the SA9904B increment at

a rate of 320 000 counts per second at rated metering

conditions for a sine wave. A single count of the active register

corresponds to an amount of energy expressed in Watt

seconds (Ws).

Energy per count is (Ws):

Epc = Vnom x Imax / 320 000

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