Pull-up resistors
Pull-up resistors
The 6502 requires 3K pull-up resistors on /IRQ, /NMI, etc. according to my sources. However, I went to my local IC supply store and asked for 3K pull-up resistors, and the salesman didn't even know what those are, and I looked at my Jameco catalog, and it didn't say `pull-up resistors' anywhere. Can someone help me find those?
Sam
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"OK, let's see, A0 on the 6502 goes to the ROM. Now where was that reset vector?"
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"OK, let's see, A0 on the 6502 goes to the ROM. Now where was that reset vector?"
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GARTHWILSON
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"Pull-up" just refers to what they do in the particular application. If nothing is shorting the IRQ line to ground (eg, one of the ICs that can request interrupt service), then the line will float up to Vcc because of the pull-up resistor.
I don't know why they always recommended 3K. The exact value is not so critical that you can't use a standard 10% value. 3.3K will work fine and is easier to get. If you ask at your "local IC supply store" (as you put it), their next question will probably be "What wattage?" Any wattage will do. 1/4 will probably be most commonly available and inexpensive. Another question might be "What type?" Carbon film is most common and will be fine. Carbon composition is also fine.
I don't know why they always recommended 3K. The exact value is not so critical that you can't use a standard 10% value. 3.3K will work fine and is easier to get. If you ask at your "local IC supply store" (as you put it), their next question will probably be "What wattage?" Any wattage will do. 1/4 will probably be most commonly available and inexpensive. Another question might be "What type?" Carbon film is most common and will be fine. Carbon composition is also fine.