For the most part, manufacturers mark their parts with part numbers which are reasonably standard throughout the industry. This makes it easy to tell what the part is, and therefore, what it does. However, if a customer buys enough of a particular part, they can get it marked with their own internal part number. These numbers usually have absolutely nothing to do with the industry-standard part numbers, which can make it rather hard to figure out what the part might be doing. There are ways to figure it out, although they usually involve looking at circuit diagrams along with some guessing.
There are a total of 11 integrated circuits mounted on the top of the PCB. They are labeled:
IC101 IC201 IC301 IC302 IC303 IC304
IC501 IC601 IC711 IC712 IC811
The numbers are listed here in kind of a left-to-right, top-to-bottom order looking at the top of the PCB.
IC201 - TA8000F
This is a Toshiba TA8000F combination voltage regulator and microprocessor watchdog. There is a data sheet for it here. The voltage regulator uses an external 2SB1015 pass transistor. According to the 2SB1015 data sheet, it is good for up to 25 watts, which is total overkill for this application.
IC501 - 74HC32A
A very traditional bit of logic representing a quad 2-input OR gate. A data sheet can be found here.
IC303 - 27C256
Peeling back the "549US" label reveals a 27C256 EPROM (Erasable Programmable Read-Only Memory). A data sheet can be found here.
This EPROM stores the ECU code. There are a wide variety of EPROMs produced by Aprilia for different bikes, different years, and different world markets. A short list of the various EPROMs can be found here.
IC304 - TC7W00F
A dual 2-input NAND gate. This is an extra-small version of the standard quad 7400 containing only 2 gates. A data sheet can be found here.
IC301 - 68HC11G
A Motorola 68HC11G processor. Documentation can be found here.
It took me a long time to figure this one out. The part number printed on the package is not a manufacturer's part number.
One of the clues was the location of the crystal connections. For this processor, the crystal is attached to pins 44 and 45. I tried a lot of different manufacturers but no one had a crystal in that location on an 84-pin PLCC (Programmable Leadless Chip Carrier) package. While searching, I noticed that Motorola made parts that ended with the suffix "CFN" (the same as on one of the number on this part) which in Motorola-speak, identify the part as being a PLCC, which most definitely is. Even so, none of the 68HC11 variants I could find had a crystal between pins 44 and 45, as on this part. I finally found an Italian web page that listed a little-known version (to me, at least!) of the 68HC11 called a "68HC11G". This version is not even listed on the Motorola site. After downloading the doc, I found it had a crystal on the correct pins. Mystery solved!
IC601 - 4049
A standard CMOS hex inverting buffer. A data sheet can be found here.
IC101 - 74HC02
A standard quad 2-input NOR gate. A data sheet can be found here.
IC302 - 4052
An analog multiplexer. Motorola refers to them as an MC14052. A data sheet can be found here.
IC712, IC711 - TLC274A
A CMOS "Precision Quad Op Amp", according to Texas Instruments. The data sheet can be found here.
IC811 - ???
There are no markings at all on this chip. I know that it is an air pressure sensor chip, if only because it looks like one. In addition, we already know from the published wiring diagrams that the ECU has a MAP sensor to measure the pressure in the intake tract. A MAP sensor is useless without another pressure sensor to measure the ambient air pressure, so this must be it.
This PNP power transistor is used as the main pass transistor for the ECU's 5.0V regulated power supply. A data sheet can be found here.
These are the main NPN power transistors used to drive the ignition coils. I cannot find a datasheet for this specific part since it has been obsolete for many years now. The only data I could find is that a 2SD2350 was an NPN Darlington transistor with a VCE rating of 300V and a collector current rating of 6 Amps. That said, I was able to find some old cross-reference data for substitute parts. In particular, the following parts are listed as being substitutes (click a link for a datasheet):
Both of those parts are NPN Darlington solenoid/coil driver transistors with built-in protection circuitry to manage the inductive kickback. Here is an example of the internals for the 2SD1113 where you can see the protection circuitry:
According to the 2SD1071 datasheet, the zener diode between pin 1 (base) and pin 2 (collector) has a breakdown voltage of 300 Volts. That means that if pin 2 ever exceeds 300V, the diode will start conducting current from pin 2 into pin 1 which turns on the primary transistor on the left, which then turns on the secondary transistor on the right, which then shorts the high voltage from pin 2 (collector) to pin 3 (emitter), thus protecting the secondary transistor from being fried by the over-voltage. The big diode on the right protects the transistor if pin 3 (emitter) should ever have a positive voltage with respect to pin 2 (collector).