Question on SIP Resistors

[cbmeeks]

Assuming I want to use SIP resistors....when do I know to use isolated vs. bussed?

Isolated seems to be better for things like pull-up pins on the 65c02 that could possibly be pulled down like the RESET pin.

But maybe bussed if I have a bunch of pull-up pins that will never alter state. Like the pull-up pins of the 65c02 that I know will never go low for a particular design.

Does that logic seem sound?

Thanks!

[jac_goudsmit]

cbmeeks wrote:

Assuming I want to use SIP resistors....when do I know to use isolated vs. bussed?

It's very simple: Resistor packs (or resistor arrays or SIP resistors as you call them) are the same as regular resistors.

If you have a situation where you need a "large" number of resistors tied to a single point (such as pull-up resistors for e.g. the IRQ, NMI, RDY, SO and BE pins on a 65C02), you use the "bussed" version because you'll have to deal with fewer pins: one end of each resistor is tied to a single pin so you'll have n+1 pins for n resistors.

In some cases you can't use the bussed kind, for example my early Propeddle designs had the 6502 running at 5V and the Propeller at 3.3V and there were isolated resistor packs (not DIP but SIP) to connect the 5V data bus to eight 3.3V pins on the Propeller. Obviously in that case I wouldn't want one end of each resistor connected together! These packages use 2n pins for n resistors.

You can use the isolated resistors in a schematic where a bussed resistor pack is needed (you would need to connect one end of each resistor in the pack together), but obviously not vice versa.

===Jac