In my project, I want to use two PORTS of 8 bits for output (I believe that setting a PORTB=0xff, would be faster than PORTB.A0=1, PORTB.A1=1.....PORTB.A7=1?)
I want to use the onboard serial mode, so this means that C6 and C7 cannot be used above (as would need to be left bi-directional). This leaves A0-A5, E0-E2, B0-7, C0-5, D0-7
However, I would like to be able to program using ICSP, which unfortunately uses D6 and D7 as PGC and PGD.
I will be using the Microchip ICD2 to in-circuit program, however given the nature, I do not believe that I will be able to debug, so this is not an issue.
These (PGC and PGD) pins, I am looking to attach to an M74hc374b1, I think that these are high impedance pins, so, as long as I am pulling MCLR to VDD with a resistor, they should be usable as normal IO pins, and whilst programming it should be 'safe' to leave them connected to the M74hc374?
I think the datasheet is available here: http://www.datasheetarchive.com/pdf-datasheets/Datasheets-20/DSA-388285.pdf
I think that it should work, but the datasheet specifies that there will be a 10pico farad input max capacitance on PGC and PGD in this layout (possibly 60pico farads max in the layout I am thinking about). The ICD datasheet specifies there must be no diodes on PGC/D, which I think this is not in contradiction to. I would rather not have to jumper PGC and PGD if I can avoid it, space is going to be a premium.
Edit:
Unless someone can tell me that using A0-A4 +E0-3 would be no extra assembly instructions, just more of a pain to program
I want to use the onboard serial mode, so this means that C6 and C7 cannot be used above (as would need to be left bi-directional). This leaves A0-A5, E0-E2, B0-7, C0-5, D0-7
However, I would like to be able to program using ICSP, which unfortunately uses D6 and D7 as PGC and PGD.
I will be using the Microchip ICD2 to in-circuit program, however given the nature, I do not believe that I will be able to debug, so this is not an issue.
These (PGC and PGD) pins, I am looking to attach to an M74hc374b1, I think that these are high impedance pins, so, as long as I am pulling MCLR to VDD with a resistor, they should be usable as normal IO pins, and whilst programming it should be 'safe' to leave them connected to the M74hc374?
I think the datasheet is available here: http://www.datasheetarchive.com/pdf-datasheets/Datasheets-20/DSA-388285.pdf
I think that it should work, but the datasheet specifies that there will be a 10pico farad input max capacitance on PGC and PGD in this layout (possibly 60pico farads max in the layout I am thinking about). The ICD datasheet specifies there must be no diodes on PGC/D, which I think this is not in contradiction to. I would rather not have to jumper PGC and PGD if I can avoid it, space is going to be a premium.
Edit:
Unless someone can tell me that using A0-A4 +E0-3 would be no extra assembly instructions, just more of a pain to program
Last edited: