In my weekend quest I have gotten to the point of testing the ROM. My EPROM tool doesn't recognize then little 2K jobbers so I made a cartridge for my TI to read the contents of them.
Address lines and data lines are mated correctly. I have CS0 tied low and CS3 tied high. CS1 is connected to the computers *CE line for the cart space. Without a ROM in the ZIF I read zero's across the space (what I expected.) With a ROM installed (Only tried 1 and only for a brief moment just in case) I read 255 on each byte.
I do not have the data lines buffered as I think the ROM should drive the buss (and it appears it is hence the 1111 1111's I am seeing.
Now I need help in interpreting what I am seeing.
Is $FF on all locations (or the 20 or so I watched go by) a good indication of a faulty ROM ?
Is my problem perhaps related to the ROM's inability to drive the buss directly ?
If access time were an issue on the ROM's I would expect the data to be at least somewhat random. Am I wrong here?
I would rather not test any others until I am a little more confident in this methodology.
Finally the ROM pin outs as I am using them. Gosh I hope these are correct.
1-8 A7-A0
9-11 D0-D2
12 GROUND
13-17 D3-D7
18 CS0
19 A10
20 CS1
21 CS3
22-23 A9-A8
24 +5V
Thanks.
Marc
Address lines and data lines are mated correctly. I have CS0 tied low and CS3 tied high. CS1 is connected to the computers *CE line for the cart space. Without a ROM in the ZIF I read zero's across the space (what I expected.) With a ROM installed (Only tried 1 and only for a brief moment just in case) I read 255 on each byte.
I do not have the data lines buffered as I think the ROM should drive the buss (and it appears it is hence the 1111 1111's I am seeing.
Now I need help in interpreting what I am seeing.
Is $FF on all locations (or the 20 or so I watched go by) a good indication of a faulty ROM ?
Is my problem perhaps related to the ROM's inability to drive the buss directly ?
If access time were an issue on the ROM's I would expect the data to be at least somewhat random. Am I wrong here?
I would rather not test any others until I am a little more confident in this methodology.
Finally the ROM pin outs as I am using them. Gosh I hope these are correct.
1-8 A7-A0
9-11 D0-D2
12 GROUND
13-17 D3-D7
18 CS0
19 A10
20 CS1
21 CS3
22-23 A9-A8
24 +5V
Thanks.
Marc
