How many I/O per chip?

Dave E

Senior Member
I was updating my Picaxe quick reference chart for the M2 chips when I noticed that I was only able to count 16 I/O pins on the 20M2 instead of the 18 listed on the web site. Can the serial IN and OUT pins be used for an input only and output only pin like the other M2 chips?

This got me to checking and I found a similar situation with the X2 chips.
I can only locate 17, 21 and 32 I/O pins on the pin out drawings for the 20X2, 28X2 and 40X2 yet the specification grid on the web site list 18, 22 and 33 I/O pins.

It seems like I have seen the answer to this somewhere but am unable to recall it from a forum search.

Thanks,
Dave E
 

Technical

Technical Support
Staff member
We realise there is some discrepancy in places that we are working to fix, but if the download pins also support the serrxd and sertxd commands (as with all M2 and X2 parts) they are considered an i/o pin, as they can send and receive data via the end-user BASIC program.
 

Dave E

Senior Member
Let's sum things up

Thanks for the input.

So to sum things up:

All M2 and X2 program download input pins (Serial In) can also be used for user defined serial input.
All M2 and X2 program download output pins (Serial Out) can also be used for user defined serial output.

For the 08M2, 14M2 and 18M2 chips the Serial In pins can also be used for a digital (on or off as in a button input) input only pin and the Serial Out pins can also be used for a digital (on or off as in driving an LED) output only pin. The 20M2 does not have this feature.

For the X2 chips, the Serial Out pin can also be used for a digital (on or off as in driving an LED) output only pin.

Please confirm that my understanding is correct.
Dave E
 

hippy

Technical Support
Staff member
My understanding is -

Code:
[b]Serial Input Pin[/b]

                08M2    14M2    18M2    20M2    20X2    28X2    40X2

SERRXD          Yes     Yes     Yes     Yes     Yes     Yes     Yes
General input   Yes     Yes     Yes     No      No      No      No
Code:
[b]Serial output pin[/b]

                08M2    14M2    18M2    20M2    20X2    28X2    40X2

SERTXD / DEBUG  Yes     Yes     Yes     Yes     Yes     Yes     Yes
General output  Yes     Yes     Yes     No      Yes     Yes     Yes
 
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