PM9904BPD datasheet(7/22 Pages) SAMES

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PM9904BPD

Firmware

The micro-controller’s code was created according to the

guidelines set out in the evaluation software section. It is

presented as a kick-start to experimentation with the micro-

controller module and as such shouldn’t be seen as the best

(or only) possible implementation. The code was generated

using Hi-Tech PIC C (v7.86PL4); the demo version on their

www site (www.htsoft.com) is sufficient for experimentation.

The program flow is presented in Figure 9.

SPI

Bit-banging SPI is used to aid portability to other micros, i.e.

three port pins under direct software control creates

SPI_CLOCK, MOSI and reads MISO. The SPI access of the

SA9904B is divided into two tasks namely, fast and slow

changing data. This is accomplished via an interrupt driven

time-slicing architecture, with a basic timer tick of 10ms.

Rate LEDs / opto-outputs

The 10ms pulse widths on these outputs are derived from the

basic timer tick.

Creep

The creep algorithm is simply: - if the time between two

successive pulses is greater than a predefined maximum, the

respective energy accumulator is cleared. The simplest

method of deciding what the predefined value should be is to

measure the time between two pulses at the lowest

permissible load current, this is then expressed i.t.o basic

timer ticks.

User Interface

A simple interface has been implemented using two of the

three available keys. The Enter Key toggles display of

consumed kWh and kVARh units. The Down Key displays per

phase voltage and frequency data, each press shows the next

phase’s data.

Memory Usage

ROM:

4070 words

or 50% of the total capacity

RAM:

Bank

86%

Bank

26%

Bank

83%

Bank

---

or 50% of the total capacity

Please refer to the readme. 1st file for any updated information

not contained in this application note. The mentioned file is

part of the source code that accompanies this module.

Figure 9: Program flow

START

/* Switch Power on */

Setup Ctrler’s ports and interrupts

init()

boot_scrn()

interrupt service routine:

10ms ticks

ctrl fast & slow tasks

ctrl pulsing of rate LEDs

Manage interrupt on key-

press

isr()

Read energy

registers

process_a_data()

process_r_data()

/*Power off*/

END

Read voltage and

frequency registers.

User Interface

Displays the start-up screens on LCD

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