LSPC Line Sprite Processor (Neo Geo AES)

the lspc, know as the line sprite controller, is responsible for generating the signals required to output video signals it is linked with the neo g0 (or 74ls245 transceivers) for palette ram and memory card access, as well as through the cxa1145 for video output the lspc and neo b1 (graphics processor) communicate between the px lines the data pins (d0 15) send data to the neo g0 / transceiver which then controls the cxa1145 if you use an ossc and rgb output, you can observe the lcd screen on the ossc for rgb video output if the lspc is working and you have good power rails, the frequency should lock in at 59 04hz or there abouts if there are any pins shorted on the d0 15 pins, it will cause the 59 04hz to flicker on and off constantly on the ossc (the same as it would with under voltage) testing d0 15 activity as a basic check the lspc is working, it is easy to just probe the d0 15 pins (almost always the first pins around pin 2 to 30, depending on revision) turn on the console with all components installed, and probe the pins 2 to 30 on the lspc looking for basic pin activity if you see activity on most pins you can generally assume the lspc is running if you have a bad z80 cpu, 68k, work ram, bios or other things, you will not be able to check the lspc activity on d0 15 pins as it requires those to work however, you can check all other pins of the lspc even in reset without any processors, ram or bios present fv video ram activity the lspc uses fv video ram of cxk5863p (28 pin) or cxk5814p (24 pin) sram the address and data pins connect to the lspc on the cx and fx pins (or on early revisions labelled fv ax and fv dx ) turn on the console and monitor for general activity on these pins if you do not see activity, its likely your lspc is dead or has shorts on it, or is missing power or clock signals if you hold reset while powering on, the pins should show random data if you do not hold reset, and you have no game in, it should show solid data (for blue or white screen depending on bios and state of console) sv video ram activity the lspc uses sv video ram of upd43256 or cxk58257ap sram the address and data pins connect to the lspc on the bx and ex pins (or on early revisions labelled sv ax and sv dx ) turn on the console and monitor for general activity on these pins if you do not see activity, its likely your lspc is dead or has shorts on it, or is missing power or clock signals if you hold reset while powering on, the pins should show random data if you do not hold reset, and you have no game in, it should show solid data (for blue or white screen depending on bios and state of console) card interface processing path the card interface pins also come into the video processing path is different based on revision but in general have two main paths neo g0 if the console has the neo g0 chip onboard then the flow is as follows lspc (d0 15) > neo g0 (a21 38) > 74ls273 flip flop (pair) > resistor ladder 0 > cxa1145 > av port 74ls245 if you have an early revision the neo g0 is simply replaced with a transceiver typically on the far right side of the board lspc (d0 15) > 74ls245 (pair) > 74ls273 flip flop (pair) > resistor ladder 0 > cxa1145 > av port