PIC18F8720 PORTD problem

[nverma]

Hi,

I'm trying to read PORTD on the PIC18F8720 and it just doesn't work. I have set the memcon.7 = 1 to enable it to read, but nothing seems to be working on that PORT. I have also set the TRISD register for inputs. What am I missing?

[Charles Linquis]

Make certain that PSPCON is set to "0".

[nverma]

Thanks, but that doesn't help either. The problem is still there. However I notice that the PIC only reads the input once at the time of reset and not after that in the loop I have. Also I notice that there is voltage drop on the inputs connected to PORTD. Instead of reading +5V(high) when they are on, the read +2.5V. Why is there a voltage drop? I think I have accounted for the MEMCON.7 = 1 and the PSPCON.4 = 0 and set the TRISD = %11111111.
Even after this, it still doesn't read on ever occurance of the loop. The PIC has to be reset for it to read the present inputs. Please help!

[mister_e]

schematic?

Code?

[nverma]

DEFINE OSC 20
DEFINE ADC_BITS 10
DEFINE ADC_SAMPLEUS 25


INCLUDE "MODEDEFS.BAS"
INTCON.7 = 1
MEMCON.7 = 1
PSPCON.4 = 0

TRISD = %11111111

channel var byte
outputAB VAR BIT
ch_onoff VAR BIT
SYSEN VAR BIT

CHANNEL = 0
OUTPUTab = 0
CH_ONOFf = 0
SYSEN = 0

loop:

channel.bit0 = PORTD.0
channel.bit1 = PORTD.1
channel.bit2 = PORTD.2
channel.bit3 = PORTD.3
channel.bit4 = PORTD.4
channel.bit5 = 0
channel.bit6 = 0
channel.bit7 = 0

outputAB = PORTD.5
ch_onoff = PORTD.6
SYSEN = PORTB.7

pause 500

serout PORTB.4,N9600,["Channel = ",#channel,13]
serout PORTB.4,N9600,["Output AB ",#outputAB,13]
serout PORTB.4,N9600,["Channel ON/OFF = ",#ch_onoff,13]
serout PORTB.4,N9600,["SYSEN = ",#SYSEN,13]


goto loop

end

[skimask]

DEFINE  OSC	20
DEFINE ADC_BITS 10
DEFINE ADC_SAMPLEUS 25
INCLUDE "MODEDEFS.BAS"
intcon.7=1:memcom.7=1: pspcon.4:trisd=$ff:channel var byte
outputab var bit:ch_onoff var bit:sysen var bit:channel=0: outputab=0
ch_onoff=0:sysen=0
loop:
channel=portd:channel=channel & $1F: outputAB=portd.5:ch_onoff=portd.6
sysen=portd.7:pause 500
serout portb.4,n9600,["Channel = ",#channel,13,"Output AB ",#outputAB,13,"Channel ON/OFF = ",#ch_onoff,13,"SYSEN = ",#SYSEN,13]
goto loop
end

Which revision of the '8720 do you have?
The early ones had REAL, documented problems running above 4Mhz. The problems varied and depended mainly on the code running, some things worked fine, others didn't. Try running your program at 4Mhz or less once and see if it works.
I had issues with the early ones awhile back, couldn't figure it out. Read the errata sheets about the 4Mhz problem. Tried running programs at both 4Mhz and 10Mhz...4Mhz worked, 10Mhz didn't, and this was only blinking LEDs.
After I got a few of the new revisions, the problems went away.
And I simplified your program a bit...