You mean resister r135?? (Fingers crossed)....
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GBA1000 rev4 Build Log
- Thread starter BloodyCactus
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You mean resister r135?? (Fingers crossed)....
Look at the schematics, there's no guesswork to this. The output of the oscillator goes through R122 to become CPUCLK. It is also fed as an input to the 7474 D-Type flip-flop at IC78, one of the outputs of which goes through R135 to become CPUCLK.
Therefore, since we know 100Mhz is much too fast for the CPU, if using a 100Mhz oscillator then the signal needs to be halved. You therefore remove R122 and fit instead R135 meaning the CLK signal comes out of the oscillator, through the flip flop, where it is halved and then through R135 to the CPUCLK line. If, on the other hand you are using a 50Mhz oscillator the clock signal can be used directly. To do this, fit R122 and remove R135 therefore instead bypassing the flipflop and routing the clock signal directly. Simple.
And hopefully I've got that right
Look at the schematics and understand the circuit. Double check that you agree with what I'm saying.
Therefore, since we know 100Mhz is much too fast for the CPU, if using a 100Mhz oscillator then the signal needs to be halved. You therefore remove R122 and fit instead R135 meaning the CLK signal comes out of the oscillator, through the flip flop, where it is halved and then through R135 to the CPUCLK line. If, on the other hand you are using a 50Mhz oscillator the clock signal can be used directly. To do this, fit R122 and remove R135 therefore instead bypassing the flipflop and routing the clock signal directly. Simple.
And hopefully I've got that right
Look at the schematics and understand the circuit. Double check that you agree with what I'm saying.
Look at the schematics, there's no guesswork to this. The output of the oscillator goes through R122 to become CPUCLK. It is also fed as an input to the 7474 D-Type flip-flop at IC78, one of the outputs of which goes through R135 to become CPUCLK.
Therefore, since we know 100Mhz is much too fast for the CPU, if using a 100Mhz oscillator then the signal needs to be halved. You therefore remove R122 and fit instead R135 meaning the CLK signal comes out of the oscillator, through the flip flop, where it is halved and then through R135 to the CPUCLK line. If, on the other hand you are using a 50Mhz oscillator the clock signal can be used directly. To do this, fit R122 and remove R135 therefore instead bypassing the flipflop and routing the clock signal directly. Simple.
And hopefully I've got that right
Look at the schematics and understand the circuit. Double check that you agree with what I'm saying.
Martin I'll don't understand any circuit But I sure can build P.C.B's, and I'm sure your right (If it goes poof I'll blame you LOL), as for my board. I have a 50Mhz processor fitted, so the oscillator is 100Mhz and R135 is fitted (Clock speed will then be 50MHz). Correct eh???, and what jumpers need to be closed on the board......
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Nope I haven't hooked up the floppy drive as the ribbon cable ain't long enough, so what I can do is reprogram the LSI chip with my new USB programmer. Also I'll redo the gals..
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I will need to dig out the manual and work my way through all the jumper settings to properly try and help - there are quite a few. I take it you have the English translated manual?
Initially, have you checked that the correct clock signal is getting to the CPU with a scope and checked all your voltages at the chips with a meter?
Initially, have you checked that the correct clock signal is getting to the CPU with a scope and checked all your voltages at the chips with a meter?
BloodyCactus
Member
All I remember is for 50mhz cpu you need 100mhz clock
That's what I have. A 100mhz clock for my 50mhz processor.....
@britlord
Here's link that tells you in what order to troubleshoot your board. In case you haven't read it before.
http://bigbangtech.com/gba1000-recommended-build-order-for-troubleshooting/
Here's link that tells you in what order to troubleshoot your board. In case you haven't read it before.
http://bigbangtech.com/gba1000-recommended-build-order-for-troubleshooting/
Yea I been there. However, I did reprogram all the gals and although each one that I did was verified by the program after programming (Passed). When I compare whats in the chip to the buffer. I get is ERROR at line 1 (0000), and that happens on all the Gals after programming them. In other words I can't save whats in the chip, so I can compare it the buffer (I'm not sure if the gal's are programed correctly or not)...
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It's not absolutely necessary to use a 100Mhz Quartz to run the board at 50Mhz.
To test your board, you should first try with a 40Mhz Quartz as 50 can give some more troubles... Only when working at 40mhz, then try at 50mhz.
There is 2 possibilities with the quartz :
- Quartz at 50Mhz (IC78 not soldered and R122 soldered),this option is working with my board, you have to use a good CPU and a good quality quatrz,
- Quartz at 100mhz (IC78 has to be soldered on the bottom side of the motherboard and not R122, instead R135),
If you want to work with a 060 at a later point, then you should just try your board with 40mhz and not bother with the 50mhz/100mhz quartz. With the turbo board, you must take the 50mhz/100mhz quartz out of the board as the clock is generated from the 060 card. And you also can't use the 060 board if you have IC78 soldered....
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in my first test i used 80Mhz quartz from my apollo1240 with r122 and r135
verify if the jumper for kickstart is in the right position and remove jumper near slot zorro for disable ide and fastram
the fatagnus is a 318069-10 or -11?
verify if the jumper for kickstart is in the right position and remove jumper near slot zorro for disable ide and fastram
the fatagnus is a 318069-10 or -11?
I would suggest that if you have done what was discussed above (100Mz clock going through the divider circuit, R135 fitted, R122 not fitted) then we can assume the clock is good for now and review everything elsewhere for the moment.
I'm suspicious of the completely black screen...
What is your monitor connected to? The 23pin RGB port or the 8-pin DIN VGA port? If it is the VGA port, well, for starters, try a 15.75Khz monitor on the DB23 port initially, but when you do use the VGA port you need to make sure all the signals have jumpers fitted to bridge the graphics card connector. We can come to that when we know which port you are using.
I'm suspicious of the completely black screen...
What is your monitor connected to? The 23pin RGB port or the 8-pin DIN VGA port? If it is the VGA port, well, for starters, try a 15.75Khz monitor on the DB23 port initially, but when you do use the VGA port you need to make sure all the signals have jumpers fitted to bridge the graphics card connector. We can come to that when we know which port you are using.
martin. I'm using a Amiga monitor on the DB23 port. The fat agnus is a 390544-11 (PAL) Oh if I lift the board a little, then I get tiny white dots on the black screen too (Don't know if that helps)
Oh. The 100Mz clock is going through the divider circuit, R135 fitted, R122 not fitted....
Martin. If I can't get the board to work. ERRR could I send to you for diagnostic....Please....
Oh. The 100Mz clock is going through the divider circuit, R135 fitted, R122 not fitted....
Martin. If I can't get the board to work. ERRR could I send to you for diagnostic....Please....
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