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).
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.
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).
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).
The card interface pins also come into the video processing path is different based on revision but in general have two main paths.
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
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
