Break the project down into little pieces.
You can see there needs to be a ASCII receiver. (UART) There should be lots of examples on the internet. Most UARTs 16x over sample. You can build one that 2x over samples. You need to get two ASCII charters and hold them in a register.
It looks like you need a clock that is 256khz. Did I do that right? In 1mS you need to have 256 clocks.
I think you need a 9 bit counter.
At "time-0" set the output.
At count = 100 hex + ASCII_Value, reset the output.
At time = 1FF hex reset the counter and wait.
(bit 9=1, bit8:1= ASCII_Value)
This should out put 1 for 1mS + Value.
It looks like ASCII_Value needs to "mux" between Value_first and Value_last.
Just build something and see what happens. Example: build the UART and bring the 8 output out to LEDs and see what happens.