Falcon doesn't initialize blank screen

[sdisla]

I got your instructions clear, you suggested to replace the RAM *Memory Board*
If it works the ROM code being executed will check for the cartridge being present activating the ROM4 or ROM3 then I will probe the two test points on the cartridge port and use the Diag-Cart to access these two pins easily.

I meant replace as in "put it back" in the machine. The RAM board was removed whilst you tested the ROM2 CE line.

I suggested refitting the RAM board and then testing the ROM4 line (and ROM3 whilst we're at it) on the cartridge connector.

We've shown the CPU is working. We've shown ROM is being selected. Does the cartridge start to be selected too?

If all three happen, we're halfway to getting the diagnostic cart working.

BW

BW,

No activity on ROM4 or ROM3 after probe these two pins on the extension cart.

Thank you for replying.

[Badwolf]

No activity on ROM4 or ROM3 after probe these two pins on the extension cart.

Thank you for replying.

Oh wow. That's significant. But I'm not sure how.

Here are the first couple of dozen lines of TOS404 disassembled:

Code: Select all

00000000 : 602e                BRA      $00000030
00000002 : 0404 00e0      SUBI.B   #$E0,D4
00000006 : 0030 00e0 0000 ORI.B    #$E0,+0(A0,D0.W)
0000000c : 0000 8f9a      ORI.B    #$9A,D0
00000010 : 00e0                ???
00000012 : 0030 00e4 9424 ORI.B    #$E4,+36(A0,A1.W)
00000018 : 0308 1993      MOVEP.W  $1993(A0),D1
0000001c : 00ff                ???
0000001e : 1a68                ???
00000020 : 0000 56ba      ORI.B    #$BA,D0
00000024 : 0000 1187      ORI.B    #$87,D0
00000028 : 0000 6ee4      ORI.B    #$E4,D0
0000002c : 0000 0000      ORI.B    #$00,D0
00000030 : 46fc 2700      MOVE.W   #$2700,SR
00000034 : 3038 8006      MOVE.W   $00008006,D0 
00000038 : 4e70                RESET     
0000003a : 3038 8006      MOVE.W   $00008006,D0 
0000003e : 31fc 0007 8940 MOVE.W   #$0007,$00008940 
00000044 : 0cb9 fa52 235f 00fa 0000 CMPI.L   #$FA52235F,$00fa0000
0000004e : 660a                BNE      $0000005a

Address 0 says jump to address 30.

Address 30 turns off interrupts and goes into supervisor mode.
Address 34, 48 and 3a are the special Falcon incantations to reset the peripherals.
Address 3e appears to set the GPIO pins on the DSP port -- don't worry about that one.
Address 44 performs a double read of the cartridge port.

So exactly seven instructions into ROM, the cartridge port should be activated. Things are going wrong very early.

Do you see the second reset pulse? If you probe the reset pin (on the expansion connector is easiest) you should see it go high about 400ms after you release the reset button and very rapidly (within a few microseconds) there should be another obvious short pulse (that command in address 38, above).

If you don't see that either then it could be a problem with the ROM or, more likely, something interfering with the address or data lines so that what comes back from the ROM isn't understood.

BW

[sdisla]

BW,

At this point you think that the VIDEL chip needs to be replace or still to early in the game to determine that?

Thank you,

[Badwolf]

BW,

At this point you think that the VIDEL chip needs to be replace or still to early in the game to determine that?

Thank you,

That would be probably a last resort, IMO.

You've not identified what the problem is yet, let alone the cure!

What makes you think it's Videl from the evidence you've gathered so far?

BW

[sdisla]

BW,

At this point you think that the VIDEL chip needs to be replace or still to early in the game to determine that?

Thank you,

That would be probably a last resort, IMO.

You've not identified what the problem is yet, let alone the cure!

What makes you think it's Videl from the evidence you've gathered so far?

BW

BW,

DAC is showing some garbage, COMBEL is not switching from 8MHZ to 16MHZ and Floppy LED is not showing any activity during the boot process. Reset circuit mechanism is working because at least the signal on the processor goes down while the reset button is press.
But maybe I’m missing something that you see that I don’t.

Does anyone have a pdf version of the schematic that is searchable?
At least no to waste 30 mins looking for a component?
Any cheat Sheet with values measured from a good working board?

For the settings on the Serial Port flow control options should be none, correct?

Finally, there is some feedback “garbage vvv” from Tera Term... Flow control set as "none"

ROM3 & ROM4 PIN 31 & PIN 33 always Hight 5v if reset is press is hard to tell if there is any changes.

If you keep reset press 5v never change, always Hight.

[Badwolf]

There is absolutely no point trying the serial port if ROM4 never activates. The cartridge isn't being read so it can't output anything to the serial port.

Like I say, it's as if the (main) ROM isn't being read, despite it's CE signal going low.

If you remove the square TOS ROM entirely, does *anything* change?

Ideally you should be probing the AS line and one data line at a time after reset. The data lines should always be high during the first four AS assertions with no ROM in place, and that should change when you put the ROM back.

Specifically you should get:-

D15-D0 = 602e on the first activation
D15-D0 = 0404 on the second activation
D15-D0 = 00e0 on the third activation
D15-D0 = 0030 on the fourth activation

Any activations after that are likely to be unreliable if the ROM code isn't executing.

Code: Select all

D15----D0
0110 0000 0010 1110
0000 0100 0000 0100
0000 0000 1110 0000
0000 0000 0011 0000

So D1, for example, should go high-low-low-low and D5 should go high, low, high, high.


BW

[sdisla]

There is absolutely no point trying the serial port if ROM4 never activates. The cartridge isn't being read so it can't output anything to the serial port.

Like I say, it's as if the (main) ROM isn't being read, despite it's CE signal going low.

If you remove the square TOS ROM entirely, does *anything* change?

Ideally you should be probing the AS line and one data line at a time after reset. The data lines should always be high during the first four AS assertions with no ROM in place, and that should change when you put the ROM back.

Specifically you should get:-

D15-D0 = 602e on the first activation
D15-D0 = 0404 on the second activation
D15-D0 = 00e0 on the third activation
D15-D0 = 0030 on the fourth activation

Any activations after that are likely to be unreliable if the ROM code isn't executing.

Code: Select all

D15----D0
0110 0000 0010 1110
0000 0100 0000 0100
0000 0000 1110 0000
0000 0000 0011 0000

So D1, for example, should go high-low-low-low and D5 should go high, low, high, high.


BW

BW,

After checking all the AS "Adress Strobes" from A1 to A15 with the ROM inserted.
Always low with the exception of A3 which is always high.
If the reset button is press it A1, A2, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15 goes high then goes down.
If the reset button is hold on reset, it will stay high until is release again.

After checking all the AS "Adress Strobes" from A1 to A15 with the ROM removed.
Always low, as soon as reset is press it goes high regardless how many times the reset button is press.

One last thing, you said "Ideally you should be probing the AS line and one data line at a time after reset."
I missed this request so I guess I can replicate that today.
So, if I understand correctly let me see how I can manage getting two probes at the same time on the cartridge connector one AS and one Data.
Data line I checked them randomly, my bad I should check them thoroughly.
I found that with no ROM they are high, but I need to double check that.

Lastly, I will probe the data lines with the ROM inserted to see if I'm getting anything after the activations.

Hope this will help and thank you for your valuable time.

[Badwolf]

After checking all the AS "Adress Strobes" from A1 to A15 with the ROM inserted.
...
So, if I understand correctly let me see how I can manage getting two probes at the same time on the cartridge connector one AS and one Data.

I'm sorry, but you seem completely confused and not able to follow what I'm suggesting.

I'm not sure if this is a language (translation) problem or if you don't know what I'm talking about but what you're doing doesn't tie in with what I'm suggesting.

AS is Address Strobe and it's one of the pins on the CPU and therefore also on the expansion connector. The expansion connector is not the cartridge port.

You were meant to be measuring the data lines during the time AS is low for the first four AS low pulses.

That means you need to probe AS, trigger on AS and, on the other channel, probe (for example) D1.

D1 will be available on the CPU, the expansion port (and also on the cartridge port, but we've moved away from that as you've told me it never activates).

Remember, we're talking about the first four AS activations (pulses low) after reset is released.

You are trying to see if the ROM is returning the correct data to the CPU on these accesses. I have listed all of the states of the data lines for every one of these four pulses in the message above.

You can then try the same with the ROM removed as, with no ROM there to drive the data lines, they should all be high on every AS access.

The reason we're doing this is you've told me ROM4 never pulses low after reset. If you are not sure of this, go back and verify it. What you are probing and why seems very erratic and unclear to me, so I'm now concerned I'm suggesting actions based on a misunderstanding.

BW

[sdisla]

After checking all the AS "Adress Strobes" from A1 to A15 with the ROM inserted.
...
So, if I understand correctly let me see how I can manage getting two probes at the same time on the cartridge connector one AS and one Data.

I'm sorry, but you seem completely confused and not able to follow what I'm suggesting.

I'm not sure if this is a language (translation) problem or if you don't know what I'm talking about but what you're doing doesn't tie in with what I'm suggesting.

AS is Address Strobe and it's one of the pins on the CPU and therefore also on the expansion connector. The expansion connector is not the cartridge port.

You were meant to be measuring the data lines during the time AS is low for the first four AS low pulses.

That means you need to probe AS, trigger on AS and, on the other channel, probe (for example) D1.

D1 will be available on the CPU, the expansion port (and also on the cartridge port, but we've moved away from that as you've told me it never activates).

Remember, we're talking about the first four AS activations (pulses low) after reset is released.

You are trying to see if the ROM is returning the correct data to the CPU on these accesses. I have listed all of the states of the data lines for every one of these four pulses in the message above.

You can then try the same with the ROM removed as, with no ROM there to drive the data lines, they should all be high on every AS access.

The reason we're doing this is you've told me ROM4 never pulses low after reset. If you are not sure of this, go back and verify it. What you are probing and why seems very erratic and unclear to me, so I'm now concerned I'm suggesting actions based on a misunderstanding.

BW

BW,

ROM4 or ROM3 never pulses low after reset.

I will continue as you suggested, thank you for your patience.

[sdisla]

After checking all the AS "Adress Strobes" from A1 to A15 with the ROM inserted.
...
So, if I understand correctly let me see how I can manage getting two probes at the same time on the cartridge connector one AS and one Data.

I'm sorry, but you seem completely confused and not able to follow what I'm suggesting.

I'm not sure if this is a language (translation) problem or if you don't know what I'm talking about but what you're doing doesn't tie in with what I'm suggesting.

AS is Address Strobe and it's one of the pins on the CPU and therefore also on the expansion connector. The expansion connector is not the cartridge port.

You were meant to be measuring the data lines during the time AS is low for the first four AS low pulses.

That means you need to probe AS, trigger on AS and, on the other channel, probe (for example) D1.

D1 will be available on the CPU, the expansion port (and also on the cartridge port, but we've moved away from that as you've told me it never activates).

Remember, we're talking about the first four AS activations (pulses low) after reset is released.

You are trying to see if the ROM is returning the correct data to the CPU on these accesses. I have listed all of the states of the data lines for every one of these four pulses in the message above.

You can then try the same with the ROM removed as, with no ROM there to drive the data lines, they should all be high on every AS access.

The reason we're doing this is you've told me ROM4 never pulses low after reset. If you are not sure of this, go back and verify it. What you are probing and why seems very erratic and unclear to me, so I'm now concerned I'm suggesting actions based on a misunderstanding.

BW

BW,

ROM inserted.

CH1 probe on pin 4 "Address Strobe" of the 50-pin connector.

CH2 probe on pin 14 "Data 1" on 30-pin connector.
CH2 probe on pin 13 "Data 2" on 30-pin connector.
CH2 probe on pin 12 "Data 3" on 30-pin connector.
CH2 probe on pin 11 "Data 4" on 30-pin connector.
CH2 probe on pin 10 "Data 5" on 30-pin connector.
CH2 probe on pin 9 "Data 6" on 30-pin connector.
CH2 probe on pin 8 "Data 7" on 30-pin connector.
CH2 probe on pin 7 "Data 8" on 30-pin connector.
CH2 probe on pin 6 "Data 9" on 30-pin connector.
CH2 probe on pin 5 "Data 10" on 30-pin connector.
CH2 probe on pin 4 "Data 11" on 30-pin connector.
CH2 probe on pin 3 "Data 12" on 30-pin connector.
CH2 probe on pin 2 "Data 13" on 30-pin connector.
CH2 probe on pin 1 "Data 14" on 30-pin connector.
CH2 probe on pin 16 "Data 15" on 30-pin connector.

Pressing the reset button AS pulse goes high but, no pulse activity on D1,D2,D3,D4,D5,D6,D7,D8,D9,D10,D11,D12,D13,D14,D15 low state.

ROM removed.

CH1 probe on pin 4 "Address Strobe" of the 50-pin connector.

CH2 probe on pin 14 "Data 1" on 30-pin connector.
CH2 probe on pin 13 "Data 2" on 30-pin connector.
CH2 probe on pin 12 "Data 3" on 30-pin connector.
CH2 probe on pin 11 "Data 4" on 30-pin connector.
CH2 probe on pin 10 "Data 5" on 30-pin connector.
CH2 probe on pin 9 "Data 6" on 30-pin connector.
CH2 probe on pin 8 "Data 7" on 30-pin connector.
CH2 probe on pin 7 "Data 8" on 30-pin connector.
CH2 probe on pin 6 "Data 9" on 30-pin connector.
CH2 probe on pin 5 "Data 10" on 30-pin connector.
CH2 probe on pin 4 "Data 11" on 30-pin connector.
CH2 probe on pin 3 "Data 12" on 30-pin connector.
CH2 probe on pin 2 "Data 13" on 30-pin connector.
CH2 probe on pin 1 "Data 14" on 30-pin connector.
CH2 probe on pin 16 "Data 15" on 30-pin connector.

Pressing the reset button AS pulse goes high but, no pulse activity on D1,D2,D3,D4,D5,D6,D7,D8,D9,D10,D11,D12,D13,D14,D15 low state.

Thank you,