Round Instruction
The Round instruction is meant to round the accumulator to 34
fractional bits, by adding 1 at bit 36 if bit 35 is 1. I managed to
implement this without making any changes to the hardware. The strategy
is to first shift word 1 of the accumulator left by one bit (by adding
it to itself), so that bit 35 ends up in the carry flag, and then add
the carry to words 2 and 3. Finally, words 0 and 1 are cleared.
# Y - Round accumulator to 34 fractional bits
00110 0 0001 : - - 10 XAC - YAC CY0 -- - - - LSW - - - --- - --- ---- # Shift word 1 of AC left
00110 0 0010 : - - 01 XAC - Y0 -- WAC - - - - - - - --- - --- ---- # Add carry to AC words 2 and 3
00110 0 0011 : - - 11 XAC - Y0 -- WAC - - MSW - - - - --- - --- ----
00110 0 0100 : - - 00 X0 0 Y0 CY0 WAC - - - LSW - - - --- - --- ---- # Clear AC words 0 and 1
00110 0 0101 : - EOI 10 X0 0 Y0 -- WAC - - - - - - - --- - --- ----