The board used for the implementation
That kind of project needs for the implementation a programmable component like FPGA or CPLD. For my own, as I allready worked on
Xilinx products my choice was so turned on them. I decided to order a test board based on an XCS200 Xilinx Spartan III family chip.
This on embeded about 200K gates and the board has a lot of feachture for less than 150$, delivred in less than 48 hours for me !
More than the XCS200, the board has 32 x 256k of SRAM, some RS232, PS2, VGA ports, some switch, leds and seven segment displays. So it had all that I would have to start this project. The kit contains a really nice documentation on the board including component interface and timing waveforms and a nice technical document on Xilinx familly chip. The ISE software, running under Windows and Linux is also delivered.
This board will allows to get the SC91-A processor to run contected to a video screen, a keyboard as a remote computer througth an RS232 link.
XCS200 Xilinx Spartan III component
The spartan III componant used own 4320 cells that is equivalent to 200K logical gates. It also embed some other internal components as :
- 16 multiplyers 18x18 bits
- 12 16x1Kbits dual port RAM blocks usable as 12x18x1Kbits with parity, running at 200Mhz
- 30 Kbits of RAM into cells
- Frequency generator up to 325Mhz
- Optimized shift registers
Chip voltage is 1.2V
Chip price, for one unit, is about 13.5$.
Due to that specification, this product is well adapted for a project like simple-cpu. Thanks to its large capacity, the abstract
conception and the first revision of the processor won't be limited by the size of the generated code. That will help me to concentrate
my time on development and documentation more than on optimization. The optimization phase will so be done in a second step.
However, that component price is, for me, too important for a production and optimization will be necessary to optain a better price to market for SC91-A. For now, that component is really nice for the projet.