Add support for Cx4

[jeffythedragonslayer]

I want to guage demand for support for the Capcom Cx4 chip.

[vhelin]

I found this

https://wiki.superfamicom.org/capcom-cx4-hitachi-hg51b169

Any better documents about Cx4?

[jeffythedragonslayer]

In section 2.4, an "x" is an operand bit, and a "." is unused:

http://users.tpg.com.au/advlink/dsp/cx4.html

[vhelin]

Looks quite good, but I have two questions:

1. What is SS?
   

2. What is F?
   

[jeffythedragonslayer]

"Shift" and "far," I think.

[vhelin]

I got an answer to my questions from the maintainer of https://www.crazysmart.net.au/dsp/cx4.html - Here is the information:

Q1: What is SS in here? "100000SS .xxxxxxx | 80 | ADD | A, reg | Binary Addition | A = A + reg"
A1:

SS are the shift bits.

The Accumulator is shifted left either 0, 1, 8 or 16 bits.

SS
00 - no shift.
01 - shift Accumulator left 1 bit before operation.
10 - shift Accumulator left 8 bits before operation.
11 - shift Accumulator left 16 bits before operation.

maybe?
ADD A<<8, R15

Q2: What does F mean here? "000010F. xxxxxxxx | 08 | BRA | imm | Branch (Always)"
A2:

Assuming the Program Counter is 23 bits.

If the branch is taken:
The lower 8 bits of the instruction is copied to the lower 8 bits of the Program Counter.
If the 9th bit of the instruction is 0, the upper 15 bits of the Program Counter remains.
If the 9th bit of the instruction is 1, the page register (P) is copied to the upper 15 bits of the Program Counter.

[vhelin]

In section 2.4, an "x" is an operand bit, and a "." is unused:

http://users.tpg.com.au/advlink/dsp/cx4.html

This is now the working link (it seems): https://www.crazysmart.net.au/dsp/cx4.html