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hueyjones70

Atari 130XE boots to self-test

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I have an Atari 130XE that boots directly to self test. About half of the memory blocks show red. I have socketed the mmu, os, and basic chips. All of them check out OK. Star Raiders boots. All of this is after crossing the resistors that lead to the different memory blocks. With the resistors not crossed, The computer boots to a black screen.

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PIA might be the next thing to check. Also, 130XE has the EMMU which directs accesses to RAM in the 16-31K range.

 

Which memory blocks are coming up bad? Each one corresponds to 1K in adress order - the latest XEs also test extended memory with 4 bigger blocks at the end representing 16K each.

Red in blocks 17-32 could mean some problem with the EMMU. Also note that since the Self-Test ROM maps to the 20-21K area, it'll always return green on the blocks representing that 2K of RAM as it's not tested.

 

Also, Star Raiders runs as a diag mode cart and gets immediate control, bypassing powerup tests. And only uses the first 8K of RAM.

Though that said, any memory access will use 8 chips with each supplying 1 bit or 2 chips on later 4-bit DRam systems. The innermost row is the main memory, outer is extended.

Edited by Rybags

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The first row on the memory test shows a repeating sequence of G,G,G,R. It doesn't get to the extended memory. I am probably going to socket all the chips one at a time until I find the problem. I would like to know which are the most likely culprits so that I might shorten the process.

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Probably some sort of memory selection problem. But strange that only every 4th 1K block failing, I don't think the lines get inverted or anything for Ram selection.

Actually, throw Freddie into the suspect list as it is responsible for row/column select processing.

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I have picked up another non working 130XE. When I turned it on I got a blank screen so I tried the Star Raiders Cart. This time when I turned it on, I got a blue and white screen with many characters appearing and disappearing on the screen. I thought this might be an antic problem so I removed the ANTIC put in a socket and tried another ANTIC. When I turned the computer on I got a green screen and it was the same with or without the Star Raiders Cart. I then looked at the old antic chip and noticed that I had pulled up the solder ring on pin 16. Does anyone know where the trace from Antic 16 connects. I will have to remove 3 or 4 chips to follow it. It appears to go completely underneath the OS ROM chip, I can't tell if it goes completely underneath the BASIC chip or not. I don't have any schematics for the 130XE.

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I hope some electronics savvy person will answer a few questions about an electrical schematic of the ANTIC chip.

post-61328-0-60801700-1557103904_thumb.jpg

 

Why are the numbers not in the order of the pin numbers, what are do the labels inside the box represent (A15, AN1, RNMI etc)

Edited by hueyjones70

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Why are the numbers not in the order of the pin numbers, what are do the labels inside the box represent (A15, AN1, RNMI etc)

The numbers at the edge of the box will be the pin numbers of the chip. Schematic diagrams will order the pins in a logical layout, rather than a physical layout. In fact, the entire schematic will also be a logical layout that doesn't represent the physical layout of the circuit. This makes it easier to follow signals and understand the operation of the circuit.

 

The labels inside the chip represent the signal names. A0-A15 are the 16 address lines, D0-D7 are the 8 data lines, Vcc and Vss are the power supply, and then we get more specific. NMI is typically Non-Maskable Interrupt, RST is Reset, R/W is whether the bus is being read or written (usually CPU relative), HALT is an all-stop signal, usually because of a serious fault detected, unhandled interrupt, taking control of the bus from the CPU or similar. RDY is Ready, usually used to indicate that the bus is ready to start a requested transfer, or to move onto the next step of a transaction. AN0-AN2 are the three signals of a special ANTIC bus on Atari 8-bits, which are used for direct transfers between the custom chips without getting the main CPU bus involved, and are typically used during the building of the display. 0O and F0O are clock signals.

 

A bar above any signal name indicates that it's active low, i.e. it is asserted by dropping the signal level to close to 0V.

 

The general descriptions above could be improved with some specific context. I'm not particularly familiar with these systems so I can't offer much more than that.

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HALT is indeed used to indicate the CPU is giving up access to the bus in favor of ANTIC.

 

Those little “narrow-O” signals are supposed to be Greek letter Phi (ø). The FPhi0 is the the “Fast Clock” or “Fast Phi 0” signal. It’s received from the adjacent GTIA chip, which in turn generates that signal from the system clock oscillator (OSC) signal. FPhi0 is used by ANTIC internally to create the Phi0 signal, which is sent to the 6502C SALLY. SALLY then generates to the two phase system clock (Phi1 and Phi2). On the Atari, Phi2 is used to regulate basically the entire system.

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They are not in order because it's a lift from the 800XL

blueprint schematic found in the field service manual.

 

In that document, GTIA is diagrammed to the right of

ANTIC and the various common connections are neat clean

lines straight across making a better looking schematic

overall.

 

Be careful with that schematic as GTIA has Vcc and Vss

shown in the wrong positions.

 

This one as shown is much cleaner and easier to read,

otherwise it's exactly the same as the source layout.

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