28-40pin UniBoard

One might say "the MPUs", as Uniboard is designed to bring all the PIC 28 and 40 pin.Il game is simple: a single-sided is possible without special contortions of the slopes, spend 28 to 40 pin, the that allows to have the two sockets internal to one another.

OObviously you can not insert the two types of chips at the same time, but this is not just a mechanical limitation ...
You might wonder why not just use one ZIF. Here, too, the reason is simple: it would require a complicated game of jumpers to swap the 28 and 40-pin, something completely unfamiliar. Thus, it is preferred position on a plinth with tulip contacts of high quality, allowing many cycles of insertion-off.

And, on the other hand, does not even sense the change chip 6 times a day, being able to experiment with virtually all with a single component. In the case in which serves have multiple chip, the cost of the card does not affect so much more than in the convenience of having maybe one with a certain PIC and other with another or other PIC, immediately ready to use.

The board, however, both for experimentation and for development, is to start from the chips better supplied, so as not to come halfway without resources of RAM or memory program or with any port in less.
Then, in a possible production, you can play downwards, the code written and tested on a PIC with fewer resources.
In other words, having more resources in development is like having a large library for research, probably we will only use a small part of the available volumes, but if you serve a particular text here that 'we have at hand. As if we did not would be no problem.
The wiring diagram shows the pin functions and equivalence between the two packages, in order to have the perfect coincidence between the pins of the chip and pin connectors modular access to ' / O.

Thus, for example, whether it is added to a 28-pin or a 40 pin connector, the plug connector of PORTA, 1 will arrive precisely the pin RA1, and so on.

Of course, if you install a 28-pin connectors PORTD and PORTE are not used, because these ports are available only for 40-pin package.

L 'interchangeability also applies to pin ICSP / ICD for both chip 28-pin 40-pin chip for connecting the development tools jack ICSP / ICD on board establishes the right connections.

RESET circuit.

The section of the reset is quite elaborate compared to other demo board as the PIC 18F is particularly true, they have different applications: classic reset button, resistor and capacitor only pull-up resistor any component, using the pin as a GPIO But it is also possible to insert chip reset three-terminal or sub modules reset or supervision of the voltage.  This is the task a group of pins that you can incorporate these components.

In anticipation of wider opportunities for experimentation, even the pull-up resistor and 'any capacitor to ground are optionally fitted on pin. Only the reset button is welded fixedly to the circuit.

E 'thus possible the testing of all possible variety of circuits.

In addition, a jumper (JREs in the diagram) allows to separate the reset circuit by the MCLR pin in the case in which the resistance R2 of separation is not sufficient to ensure adequate insulation during programming ICD.
If desired, the R2 may be replaced by a Schottky diode for a complete separation to 'application of Vpp.

Here are some graphic details of 'area and reset the corresponding portion of the scheme:

• C12, optional, is the external reset delay capacitor (typically 0.1 uF).

• R1 is the resistance of pull-up of the external reset (typically 10 k).

• R2 is the resistance of separation between the circuit and the connection of the external reset ICSP (typically 1K, replaceable with a small Schottky)

JREs is a jumper that can completely isolate the section of the external reset from the rest of the circuit.
In particular, a 4-pin connector allows you to install an external device reset, more or less complex, for example the three terminals MCP1xx of Microchip or other similar of different manufacturers. The available 4-pin allows an immediate insertion of both models with reset pin center, and those with reset side

Obviously for the PIC must be the version with reset at low level, then MCP100, MCP102, MCP120, MCP121, MCP131 of Microchip and 33 164, 34 064, NCP300 of ONSEMI, DS1233 Maxim-Dallas, etc..

In addition, the ability to install R1 on removable pin allows you to use both devices with internal pull-up or push-pull output, both devices with open collector output / open drain.