I did that to allow more current on the clock line. I don't quite remember the reason for more current.
Maybe test your 74HTC08 or try another 23k256. If it works for me, it should work for you. Is your power supply stable? Maybe you need more capacitors on your supply. Matt. On Monday, September 10, 2012 3:56:47 PM UTC-4, PDSACAA wrote: > > Matt > Try as I may I cannot solve my problems attempting to use the 74HTC08 but > I will keep trying. > > Can I ask you a question regarding the resistor dividor networks shown in > the tutorial schematic illustrating the use of the 23k256 sram. > Two of the SPI lines ( SS and SDO) use 1.5k/3.3k resistors to step down > the voltage but for the CLK line you indicate 470/2k. > Why does this divider network differ from the other two lines. > Understanding this may just help me to see what I have done wrong using the > 74HTC08. > > As you have probably guessed my knowledge is weak on the electronics side > of things. > > Kind Regards > Dave Paxton > > On Friday, 7 September 2012 10:09:07 UTC+1, mattschinkel wrote: >> >> Sorry, I've been to busy to test anything. >> >> If your getting 0xFF there must be something wrong with the hardware or >> your connections. You do not need to do any level conversion for the SDO >> line (signal out of 235254 to the PIC). >> >> 74HCT08 will work, I've done it in the past. >> >> Matt. >> >> On Tuesday, September 4, 2012 8:16:03 AM UTC-4, PDSACAA wrote: >>> >>> Matt >>> I knocked out a board using the 74HCT08 logic IC and a LD1117V33 voltage >>> regulator to guarantee a 3.3V supply voltage to >>> the IC. >>> I jumpered together the pair of logic input pins on each of the 4 IC >>> gates and fed the PIC outputs CLK,SDO and SS >>> to 3 of these IC input pairs. Fed the 3 IC outputs to the 28K256. The >>> 28k256 SO line went straight to PIC SDI pin as before and as >>> per tutorial schematic. >>> I checked all of the IC output voltage levels using simple program to >>> raise or lower PIC pins. These seemed ok dropping to 0v >>> low or rising to 3.68V high. >>> >>> Unfortunately when running sample program to read/write 28k256 via the >>> 74HCT08, I get nothing but FF's. >>> I have checked, checked and rechecked wiring but can't find anything >>> wrong. >>> >>> I take it that it goes without saying that the 74HCT08 can switch at the >>> clock speeds the SPI routines throw at it? >>> I dropped the CLK speed down to the minimum but this showed no >>> difference. >>> Have you got any ideas where I might have slipped up? >>> >>> At least the resistor divider network worked up to a point!! >>> >>> Regards >>> Dave >>> >>> On Sunday, 2 September 2012 02:51:10 UTC+1, mattschinkel wrote: >>>> >>>> Please try the 74HCT08. The resistor divider should work as well, but >>>> 74HCT08 will give you better signals. >>>> >>>> -- You received this message because you are subscribed to the Google Groups "jallib" group. To view this discussion on the web visit https://groups.google.com/d/msg/jallib/-/RScH_oJng40J. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
