pic16f628: can't use MCLR pin for I/0! - Electronic Circuits Projects Diagrams Free

ramantas · 9th November 2003, 12:31 PM

I disable MCLR by configuration bits,
__CONFIG _INTRC_OSC_NOCLKOUT & _MCLRE_OFF

then type

movlw 0x07
movwf CMCON
bcf STATUS, RP1
bsf STATUS, RP0
MOVLW 0xff
MOVWF TRISA

but TRISA register is not affected on bit 5, and i can not use PORTA bit 5 for input. Why? Microchip datasheet says that bit 5 supports input, if you disable MCLR. Currently i am working on Mplab IDE 6.30 - the chip has the same problem, or is it a software bug? (i noticed that checking the model pic16f628A does not correct the problem)

Exo · 9th November 2003, 12:51 PM

Seems like your config word isn't assembled right

Try __CONFIG 0x3D18

ramantas · 9th November 2003, 06:08 PM

thanks for the reply, but your hint doesn't seem to solve the problem. Anyways, I am planning to connect a 4*4 keypad matrix and an LCD screen to the PIC, so the number of I/O pins is a bit of an issue. Is there anything else I could try to disable MCLR?

Exo · 9th November 2003, 06:51 PM

Did you already try it for real? or just simulation.
I burnt a 16F628A here to try and read a switch on MCLR and it works...
Maybe a simulator bug

ramantas · 10th November 2003, 08:34 AM

Well, you' ve been a great help Exo! No, i hanen't tried this for real yet (no programmer available at this time). I guess I' ll try it again on the MPLAB 6.32 interim release

justin_sane · 10th November 2003, 07:27 PM

How do you reprogram after MCLR is set to input?

Exo · 10th November 2003, 11:40 PM

By making it 14V pic will go to programmer mode - regardless of how the pin is configured

justin_sane · 11th November 2003, 02:40 AM

I program using LVP.

I guess that is out if you are operating in that mode.

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9th November 2003, 12:31 PM	(permalink)
ramantas	pic16f628: can't use MCLR pin for I/0! I disable MCLR by configuration bits, __CONFIG _INTRC_OSC_NOCLKOUT & _MCLRE_OFF then type movlw 0x07 movwf CMCON bcf STATUS, RP1 bsf STATUS, RP0 MOVLW 0xff MOVWF TRISA but TRISA register is not affected on bit 5, and i can not use PORTA bit 5 for input. Why? Microchip datasheet says that bit 5 supports input, if you disable MCLR. Currently i am working on Mplab IDE 6.30 - the chip has the same problem, or is it a software bug? (i noticed that checking the model pic16f628A does not correct the problem)

9th November 2003, 12:51 PM	(permalink)
Exo	Seems like your config word isn't assembled right Try __CONFIG 0x3D18

9th November 2003, 06:08 PM	(permalink)
ramantas	thanks for the reply, but your hint doesn't seem to solve the problem. Anyways, I am planning to connect a 4*4 keypad matrix and an LCD screen to the PIC, so the number of I/O pins is a bit of an issue. Is there anything else I could try to disable MCLR?

9th November 2003, 06:51 PM	(permalink)
Exo	Did you already try it for real? or just simulation. I burnt a 16F628A here to try and read a switch on MCLR and it works... Maybe a simulator bug

10th November 2003, 08:34 AM	(permalink)
ramantas	Well, you' ve been a great help Exo! No, i hanen't tried this for real yet (no programmer available at this time). I guess I' ll try it again on the MPLAB 6.32 interim release

10th November 2003, 07:27 PM	(permalink)
justin_sane	How do you reprogram after MCLR is set to input?

10th November 2003, 11:40 PM	(permalink)
Exo	By making it 14V pic will go to programmer mode - regardless of how the pin is configured

11th November 2003, 02:40 AM	(permalink)
justin_sane	I program using LVP. I guess that is out if you are operating in that mode.