PM9904BPD Ver la hoja de datos (PDF) - South African Micro Electronic Systems

Número de pieza

componentes Descripción

Fabricante

PM9904BPD

Evaluation Board for the SA9904B Energy Metering IC

South African Micro Electronic Systems 

PM9904BPD

THE MICRO-CONTROLLER BOARD

OVERVIEW

This section describes the plug-in micro-controller board and

should be read in conjunction with the evaluation software

section, where basic metering software is described. The

micro-controller’s software was developed according to this

section. The board plugs into the evaluation module as

described earlier in this application note.

1

Figure 7: Micro-controller board

Hardware

The schematic is presented in Figure 18. As can be seen the

major elements are:

+ micro-controller,

+ eeprom,

+ keys,

+ rate LEDs / opto-isolated rate pulse output

+ and miscellaneous connectors.

Micro-controller

A PIC 16F876-20/so is used to generate the rate pulses, in this

application the micro uses a 20 MHz crystal (X1). This device

has 8kB Flash ROM (program memory) and 368 Byte RAM

(data memory). Detail information on the device can be

obtained in the appropriate MICROCHIP datasheet.

EEPROM

A 93C46 EEPROM provides storage for non-volatile data,

such as calibration factors. This device has 1 kB space

available or stated differently 128 x 8bit words.

sames

Keys

Four keys are provided of which one is connected to the micro-

controller’s reset pin. The other three are available to

implement an HMI (Human Machine Interface) in the firmware;

they’re labelled Up/Down and Enter on the printed circuit

board.

Rate outputs

Two LEDs are provided for active and re-active energy

respectively. These pulse outputs can be coupled to an opto-

coupler via JP3/4 providing an output for external usage. This

output-pulse selection is accomplished with a jumper on JP3/4

as follows:

+

Jumper on board’s outside edge = a ctive

+

Jumper on board’s centre pins

= re -active

+

Jumper on board’s inside edge

= not used

Miscellaneous

Connectors JP1 and JP2 are provided to ease debugging

during code development, all relevant signals are available. J1

in conjunction with SK2 are the two plug-in points to the

evaluation module, where SK2 is the SPI connector and J1

merely a stabilising holder. The micro-controller is

programmed via SK1 using the controller’s ICSP (in circuit

serial programming) capability, as described in the relevant

MICROCHIP datasheet. If the intention is to program the board

from MICROCHIP’s PICSTART-programmer a buffer needs to

be inserted in the VDD line to boost the programmer’s output

capability. An example of such a buffer is shown in Figure 8.

>5V

820K

R1

100R

R3

2N3906

I/P

2N3819

O/P

1.2M

R5

820K

R2

0V

Figure 8: Typical buffer circuit

http://www.sames.co.za

6/22

Share Link: