PIC16F684 datasheet(6/13 Pages) MATRIX

6 / 13 page

Circuit description

The multiprogrammer solution is made up of two

parts: a circuit board that allows various slave PICmicro

devices to be programmed, and the Windows based

programming utility ‘mLoader’.

1. Power supply

The board is normally operated from a regulated DC

supply of 7.5 - 9V or from a USB supply. This allows full

operation including programming. The board can be

operated solely from the USB cable provided. However

care must be taken, as there is only limited power that

can be taken from a computer’s USB port.

The jumper link system, J11, allows the user to decide

on the source of the power supply. If using a regulated

7.5V power supply the jumper should be positioned to

the right hand side of the jumper system labeled‘PSU’. If

using USB power place the jumper on the left hand side

of the jumper system. LED D6 indicates that power is

correctly supplied to the board.

Please note that both USB and the PSU cables should

be removed for the Multiprogammer board BEFORE

changing the position of this jumper.

Remember that other E-blocks will have to receive their

voltage by placing a connecting wire from the“+V”screw

terminal of the Multiprogrammer to the “+V” screw

terminal of each E-Block that requires a voltage.

WARNING: Take extra care when wiring in a

power supply 12V may cause the board to run

hot.

Programming circuit

The Multiprogrammer connects to a personal computer

via the USB socket. Any USB socket on the PC can be

used. The host microcontroller is used to communicate

between the USB bus and the Multiprogrammer

circuitry. The host is connected to a network of analogue

switches formed by U4 and a charge pump circuit which

is used to multiply the operating voltage up to the 9-12V

programming voltage. This circuitry routes 0V, VDD and

VPP to appropriate pins on the slave PICmicro devices as

and when necessary.

3. DIL sockets and I/O ports

The slave PICmicro DIL sockets are wired in parallel (see

table of connections below) and the ports are fed out to

5 D-type sockets grouped in ports. These signals are also

available on a 40-way header (J5) for expansion purposes.

Other important signals can be accessed via the other

expansion header J24 (see table of connections below).

Port E has only 3 connections, which reflects the pin outs

of the various PICmicro devices themselves. When using

an 8-pin or 14-pin device it should be placed in the upper

pins of the 20-pin DIL socket as marked on the board.

Please refer to device datasheets for availability of port

outputs on each device.

NOTE: RA4 on some PICmicro devices has an open

collector output. This means that you will most likely

need a pull up resistor to be able to drive an LED etc.

Please see the datasheet on the device you are using

for further details. (Does not apply to 16F1937 device

supplied with the board).

WARNING: Only fit one PICmicro device at a time.

Inserting more then one PICmicro device will

cause programming to fail and may even cause

damage to the board or the PICmicros.

Reset push button

PB1 provides a reset by pulling the MCLR pin low. Note

that the programming chip will reset the slave PICmicro

as part of the send routine so that you do not need to

press this switch each time you send your program to

the board. If you are using a device with internal MCLR

functionality then you will have to ensure that the chip

is configured with an external MCLR to allow the reset

operation to work. Devices using the internal MCLR

configuration setting will be able to use the reset switch

as a digital input.

5. Frequency selection

By default the board is fitted with a 19.6608MHz crystal.

The crystal fits into a small socket, which allows the

crystal to be easily changed. For older Matrix TSL courses

a 3.2768MHz crystal is recommended. These frequencies

are chosen as they divide down by PICmicro prescalers

to give suitable frequencies for clock systems and for

facilitating serial communication using standard baud

rates.

The Jumper link system J18, J19 allows PICmicro devices

with internal oscillators to route the signals from the

oscillator pins through to Port A pins 6 and 7. This allows

the devices with internal oscillators to use all 8-bits of

the Port A for I/O operation.

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