---------------------------------------------------------------------------- Author : Pasi Ojala Telkontie 50 39230 Osara Written : 28.12.1991, revised 23.3.1992, 2.11.1992 Translation : 3.9.1996 Disclaimer : Although this works, I won't be responsible Distribution: Can't be distributed without the author's permission ©1991-1996 Pasi Ojala Possible comments to albert@cs.tut.fi. ----------------------------------------------------------------------------- A2320 for A500 - Royal Hacking It isn't impossible to use a flicker-fixer which needs a video slot in A500 or A2000A. There are also flicker-fixers that are installed into the Denise's socket, but videoslot cards are usually cheaper. Many so-called power-users have probably thought about getting a flicker fixer and the monitor to use it. This may have only been a dream, because his Amiga didn't support it. A2000 A-model doesn't have the other needed video slot connector and there isn't a video slot at all in A500. Getting a new machine was for a long time the only way to get better picture. The following will describe how to attach a video-slot version of the flicker fixer to these models also. Why A2320 ? A2320 is one of the best flicker fixers in the market, and not only because it is(was) made by Commodore itself. A2320 supports both PAL and NTSC screen modes and also works correctly with the biggest possible overscan (736x564). The card also automatically detects the screen mode from the signal coming from Denise. When doing video production, you can turn the flicker fixer off with the by-pass switch or use the old video monitor to look at the picture. In A2320 the Scan Line Doubling has been done correctly and there are no shadow images in non-interlaced modes. The card also detects productivity and because the signal already is in VGA-frequencies, it is passed through. Unfortunately there is too little memory to correctly de-interlace the new Super-Hires mode, and every other pixel will be lost, unless A2320 is switched off. However, the same problem is present in all the flicker fixer models. B2000 Is Needed A2320 is a great solution, but what if you have 'only' A500 or the older A2000-model, which only has half of the video slot ? No problem, you can also insert the card into A2000A, but you will only get 16 colors, because some of the color signals are in the missing connector. This can be enough in emergencies, but Real Men (tm) won't be satisfied with this. Brains in hand, soldering iron warming up, just make the motherboard accessible, i.e. open the machine and remove the disk drive and other offending parts. After this, using the schematic, determine the location of the missing signals in the motherboard (near Denise), and connect these signals to the flicker fixer card. It is best to connect the wires to the buffer chip outputs near Denise. Only eight wires need to be added to get all the necessary signals. Unfortunately the wires need to be soldered directly to the card, because there is not enough room in the motherboard to use a connector. What signals does the A2320 actually need ? The card buffers video fields in digital domain, so we need R0-R3, G0-G3, and B0-B3, i.e. the color components. In addition we need the synchronization signals _Vsync and _Hsync, and the clock signal _VC1, which can be found from the A500 schematic diagram under the name _CCKB. To work the card also needs +5V supply voltage and the ground signal. In the A2000A, most of these signals are already present in the one and only video slot connector. Installing into A2000A At least in motherboard versions 3 and 4 there are two 74HC244 buffer chips to the right from Denise. The component numbers are U77 and U78. The corresponding markings should be present somewhere near the chips, etched into the silk layer of the motherboard. Red and blue color is buffered in U78, U77 buffers the green color and the syncronization signals. Signals to wire are R0, R1, R2, G0, G1, G2, B1 and B2. The rest of the signals are present in the first video slot connector. You can use ordinary signal wire, but try to keep the total length of one wire less than 30cm. Because the flicker fixer will be installed into the video slot, you shouldn't need longer wires. Getting to the Work You better start the work by soldering the other ends of the wires to the buffer chips, and after that solder the other ends to the flicker fixer card. Red R0, R1, and R2 are soldered to U78, pins 18, 16, and 14, respectively. Green G0, G1, and G2 are soldered to U77, pings 3, 5, and 7. Blue B1 is soldered to U78 pin 5, and B5 to U78 pin 7. Remember that the numbering of TTL chips starts from the pin one, from the upper left-hand-corner of the chip (the top side or the first pin is marked with an indention) and continues counter-clockwise. R0, R1, and R2 are soldered to the second card-edge connector of the flicker fixer card, to the connections 2, 3, and 4. G0, G1, and G2 to 6, 7, and 8. Blue B1 is connected to pin 10, and B2 to pin 11. Creating a Video Slot - A500 In A500 there is no video slot at all, so the work is slightly more complicated. However, it only takes a moment for fair hardware hacker to overcome the problems. All you need is a 20-pin flat ribbon cable and an appropriate card-edge connector (at least 2x39 pins). You can also use two 36-pin (2x18) connectors or solder the wires directly to A2320. You need at minimum 17 wires, but this isn't practical. You need more ground wires (signal grounds) to minimize interferences between signals. All the necessary signals can be found from the two buffer chips behind Denise (except sync signals). See the attached table. At least in A2320 all the ground pins in the connector are connected together, so it doesn't matter which ones of these are used. For some strange reason A500 use two-directional buffers 74HCT245, U40 and U41. The direction control is just wired to the video supply voltage. One advantage is that we only need the pins on the other side of the chip, those ones further away from Denise. On the other hand, it is quite hard to solder in such a small space. My machine has a rev. 4 motherboard, so if you have other buffer chips, check your schematics before proceeding with these instructions. Raiders of the Lost Signals U40's pins 11-14 are the buffered green color signals G0-G3. Pins 15-18 hold the buffered red signals R0-R3, chip U41 pins 15-18 give out the buffered blues B0-B3. Both chip's pins 19 and 10 are connected to ground and the ground wires can be soldered to these pins. The clock signal _CCKB is in U41's pin 14. Unfortunately _Hsync and _Vsync signals are not in the video buffers. It is easiest to use the RBG connector inside the machine. Two leftmost contacts are 12=_VSync and 11=_Hsync. These lines go directly to Agnus, so you should avoid unnecessary electrical shocks. On the other hand, these lines are bi-directional, so there is some amount of protection in the Agnus chip. You should be very careful about where to take the supply voltage for the card. Take it from some of the TTL chips, but not from those video buffers, because the video supply voltage is only 4.2V. This is enough to drive the TTL chips, but the flicker fixer card probably won't work at all with this voltage, at least mine didn't. The right place could be U33's (74F04) pin 14. After this you solder the other ends of the flat ribbon cable to the corresponding pins in the 'video slot connector'. Even before soldering to the buffer chips, it is wise to do a list of the signals in the ribbon cable. Also, it is best to check the lines for short-circuits. The wires can go either directly to the flicker fixer card, or to a DB25-connector, which can be installed to the upper right-hand corner of the machine. The end result is nicer-looking and you can more easily move the machine. My suggested pin order reduces the possibility of breaking up things, even if the card is accidentally connected to the parallel port, because voltage, ground and signal lines mostly correspond each other. Also, if the same (numerical) order is used in the flat ribbon cable, there is enough signal grounds to prevent interference between signals. Try It Then just attach the card, attach a monitor to the card, and hit the power switch. If the picture comes up as normal, nothing is badly wrong. If the colors seem wrong, run a paint program and by changing the palette try to determine which bit or what bits are wrong. If there is a right kind of picture, but it won't stop in the middle of the screen, _Vsync might not be connected. If the picture is horizontally defective, check _Hsync. If the Amiga first boots normally, but after a while resets itself, either one of these sync signals may be grounded. If there is no picture, the supply voltage for the card may be too low, or there is something wrong with the monitor cable. Also check that the monitor is turned on :-) --------------------------------------------------------------------- A2000 video slot and the signals to connect in A500 A2320's Solder side Component Side 1 -NC- 2 -NC- 3 FLTLeft 4 FLTRight 5 -NC- 6 +5V U33 14 7 ARED 8 +5V 9 GND 10 +12V 11 AGREEN 12 GND 13 GND 14 _BSYNC 15 ABLUE 16 _XCLKEN 17 GND 18 BURST 19 _C4 20 GND 21 GND 22 _Hsync video 11 23 B0 U41 15 24 GND 25 B3 U41 18 26 _Vsync video 12 27 G3 U40 14 28 BSYNC 29 R3 U40 18 30 PIXELSW 31 -5V 32 GND 33 INTCLK 34 _VC1 U41 14 35 +5V 36 PSTROBE 1 GND U40 10 2 R0 U40 15 3 R1 U40 16 4 R2 U40 17 5 GND U40 19 6 G0 U40 11 7 G1 U40 12 8 G2 U40 13 9 GND U41 19 10 B1 U41 16 11 B2 U41 17 12 GND U41 10 13 BCOMP 14 IBASE 15 VCDAC 16 PPOUT 17 _VC3 18 PBUSY 19 _LPEN 20 _PACK 21 PSEL 22 GND 23 PPD0 24 PPD1 25 PPD2 26 PPD3 27 PPD4 28 PPD5 29 PPD6 30 PPD7 31 _LED 32 GND 33 RAWLEFT 34 Shield 35 RAWRIGHT 36 Shield A Suggested DB25 connector pinout (corresponds the signal order in the flat ribbon cable) 1 GND U40 10/19 2 R0 U40 15 3 R1 U40 16 4 GND U40 10/19 5 R2 U40 17 6 R3 U40 18 7 GND U40 10/19 8 G0 U40 11 9 G1 U40 12 10 GND U40 10 11 G2 U40 13 12 G3 U40 14 13 GND U40 10 14 +5V U33 14 15 _HSYNC video 11 16 _VSYNC video 12 17 GND U41 10 18 _VC1 U41 14 19 GND U41 10 20 B0 U41 15 21 B1 U41 16 22 GND U41 10/19 23 B2 U41 17 24 B3 U41 18 25 GND U41 10/19 ------------------------------------------------------------------------