28X1 Pinouts

The 28X1 pinouts shown in the new manual 1 at page 8 and again at page 28 are idential but on page 31 a different set are shown. Could someone explain why this difference and what the black figures within the chip outline on page 28 represent.

Page 8 and 28 show the conventional 28 pin DIP (dual in-line package) PIC chip.

On Page 31 the diagram is of a 28 pin carrier (akin to a B@SIC ST@MP in format).
The black boxes in the diagram represent different surface mount components such as the PIC chip, EEPROM, voltage regulator etc.
Have a look at the 28X1/X2 isometric picture and 28X2 layout on page 30 for notes on what the parts are.

I guess that the pinouts differ as the carrier based version permits Rev Ed to change the pin out and they have taken the opporunity to have all the inputs (PortC) on one side and all the Outputs (PortB) on the other side. That way we don't have half the inputs on one side and half on the other side. Instead they split the analogue inputs across the two sides.

These carrier based parts are wide socket configuaration as opposed to the narrow socket configuration for the 28X1 in DIP format so changes to the pin out are not a big issue. (Sure others will disagree here :eek:)
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Apologies for the slow acknowledgement WA but for some unexplainable reason your post sent me off at a tangent sussing out chip packages. And what a waste of time that proved to be. Apart from dimensional details in supplier's catalogues it seems the only way to gather technical information on packages is to access the appropriate standards bodies, ISO or SA. Not a relevant exercise at the moment so I'll leave it for a later task.

Is it correct to assume there are two options with the 28X1. Both in 28 pin DIL format, one encapsulated with the pinouts per page 28 of manual and the other with surface mounts unsealed and the pinouts per page 31. Apart from the perceived advantage of having inputs and outputs on opposite sides, is there a need for two versions? The local Picaxe supplier only offers the encapsulated version.


Senior Member
There are actually two OR three versions of the 28X1 depending on what is considered.

1. a 28X1 in DIL package - the 'standard' chip (narrow 0.3" DIL)
2. a 28X1 in SOIC package - has the same pinout as the DIL Both these on Page 28 Manual1 ver 6.7.01
3. a MODULE which contains a 28X1 PLUS a bunch of other components - Voltage regulator, Reset, download circuit, Resonator etc etc. - look at the picture on page 30.
This is the unit described on Page 31. This module is on a wide (0.6") format DIL.


Senior Member
That's a difficult question to answer as it all depends on what the use is.

e.g. if you can't handle soldering SOIC then that version is ruled out - otherwsie it would function the same as the DIL version, just take up less board space.

If you want to pay extra for the 'ready to go' Module to avoid the need to assemble the equivalent set of comnponents and get them working, then that could be a better choice. It won't fit any of the standard boards from Rev-Ed but might be useful as a prototyping core.

It's really a decision you would need to make depending on volume, price, what else you have, and what the uses are.
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Technical Support
Staff member
It's really a matter of choosing whichever is most suitable for your purpose. There's no definitive 'this is better than that', as different solutions may be better in differing cases.

In general, the DIP packaging of a single chip is cheap and easily usable by students and hobbyists in bread-board, on vero-board or strip-board and for fitting to PCB while single chip SOIC is perhaps suited more to those with advanced capabilities and for commercial use or where there is need for a smaller footprint package. The pre-assembled carrier modules are convenient for those who want a ready built solution only needing the connection of power and is very useful for moving between breadboards without having to construct power, reset and download circuits on each.

The SOIC 08M will also be offered as a future product in a pre-mounted carrier format (AXE230) which should suit those who need to use an 08M when space is at a premium.
The DIP version of the 28X1 is a standar PIC chip in a narrow DIP package for which RevEd has developed some starter and proto boards.

The "assembled" carrier version as shown on page 31 is wide pin version and as such will not fit in earlier starter/proto boards
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Thank you all for the discussion. It's great to have your helpful comments. I'll just stay with the 0.3" DIL package until experience demands otherwise.