p40 Transient problems
JPL
Posts: 8
Are there any known transient problems caused by switching between AUXIO and MAINIO?
I am currently using the BS2p40 to test SRAM chips. I am addressing the following:
MAINIO:
8 bit data in bus
1 bit Clock
1 bit Read/write
6 bit addr bus
AUXIO:
4 bit chip enable bus
8 bit data out bus
I am running 6 tests, All 0's, All 1's, Checkerboard, Inv. Checkerboard, Walking 1's, Walking 0's.
The more difficult tests have never given me an error.
I am having to switch to AUXIO to switch which SRAM (10 srams in 1 IC) I am using and I also have to stay on AUXIO to read the data.
On the very simple all 1's test and all 0's test I randomly have issues with the first SRAM written to. We know it is the writing problem because of trouble shooting. However, we are unable to track down exactly what the problem is.
Again, any known timing, noise, or transient issues with toggling so many pins at once on the p40 while switching between the main and auxio?
Im also having problems with a outputs on my DAC changing as the program runs when the program isn't instructed to address said outputs.
I am currently using the BS2p40 to test SRAM chips. I am addressing the following:
MAINIO:
8 bit data in bus
1 bit Clock
1 bit Read/write
6 bit addr bus
AUXIO:
4 bit chip enable bus
8 bit data out bus
I am running 6 tests, All 0's, All 1's, Checkerboard, Inv. Checkerboard, Walking 1's, Walking 0's.
The more difficult tests have never given me an error.
I am having to switch to AUXIO to switch which SRAM (10 srams in 1 IC) I am using and I also have to stay on AUXIO to read the data.
On the very simple all 1's test and all 0's test I randomly have issues with the first SRAM written to. We know it is the writing problem because of trouble shooting. However, we are unable to track down exactly what the problem is.
Again, any known timing, noise, or transient issues with toggling so many pins at once on the p40 while switching between the main and auxio?
Im also having problems with a outputs on my DAC changing as the program runs when the program isn't instructed to address said outputs.
Comments
When you switch back and forth between MAINIO and AUXIO, you're not so much changing the actual I/O pin states as changing how they're referenced.
There are actually 4 groups of I/O registers in the BS2p40, each 8 bits with a direction, output, and input register for each group. MAINIO and AUXIO are used to control an I/O bank select bit internal to the PBasic interpreter. The interpreter uses the bank select bit to select which pair of groups is used when referred to by the I/O instructions or the variables DIRS / OUTS / INS or the various named pieces of them.
Regarding the DAC issue ... You'll need to post a schematic and a listing of your program. I/O pins don't change unless there's something in your program that causes them to change.
I have seen some weird stuff happen with the BS2P40. Most of them were my fault as I was using the wrong pin on the Basic Pro. Dev.Board!
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Have you tried using some 10K or 100K pull-up or pull-down resisters on the I/O pins?