jonb@vector.dallas.tx.us (Jon Buller) (06/12/90)
Can someone tell me what the value of r3 and r7 should be? They are claimed to be clock termination resistors in the docs, but no value is given for them. If there is no "use this value and be quiet" answer, is there a way to easily figure it out? Steve's kit has them as 220 and 330 ohms, but I don't know which is which. (The process of elimination can only take one so far...) P.S. This note really is supposed to go to the whole list (unlike that last suprise 8-), but I suppose that Mr. Scolaro will probably answer this question in his usual, quick manner. Is anyone else having little problems like this also, or am I just fresh out of school (true) and just don't know better yet? Thank you all, ---------------------------------------------------------------------- Jon Buller jonb@vector.dallas.tx.us ..!texbell!vector!jonb FROM Fortune IMPORT Quote; FROM Lawyers IMPORT Disclaimer;
sverre@lars.Seri.GOV (Sverre Froyen) (06/12/90)
> >Can someone tell me what the value of r3 and r7 should be? They are >claimed to be clock termination resistors in the docs, but no value is ... > This is described in the PC532 Functional Description in Section 1.2: 330 to ground and 220 to +5V both at the far end of the clock traces. -- Sverre Froyen sverre@seri.gov, sunpeaks!seri!sverre
george@wombat.bungi.COM (George Scolaro) (06/12/90)
[In the message entitled "pc532's r3 and r7" on Jun 11, 20:29, Jon Buller writes:] > > Can someone tell me what the value of r3 and r7 should be? They are > claimed to be clock termination resistors in the docs, but no value is ???? > given for them. If there is no "use this value and be quiet" answer, > is there a way to easily figure it out? Steve's kit has them as 220 and 330 > ohms, but I don't know which is which. (The process of elimination can > only take one so far...) Actually, there are 4 resistors for termination, 2 x 220 and 2 x 330, one 220 and one 330 for each clock line (BCLK, /BCLK). The PCB only has the holes for the 330 resistors. The 220 resistors have to be soldered to the back of the board. The doc explains how to do it in the CPU SECTION first paragraph: for each clock line { 330 ohm resistor from clock to ground (holes provided) 220 ohm resistor from clock to +5V (holes not provided) } This terminates the clock traces at close to the PCB impedance and reduces reflections from the end of the trace. best regards, -- George Scolaro george@wombat.bungi.com [37 20 51 N / 122 03 07 W]