Looping and Branching

In the microcode, looping and branching is accomplished with the J, K, U and D commands, along with the P and N commands. At the outermost level in a given block of microcode, the current secondary bit in the left-hand section is in column 4. The U command is used for looping, and the D command is used for branching. The destination row of a jump (caused by the Escape command followed by U or D) is flagged with a one bit in the current column in the left-hand section. In the case of nested loops/if statements, the current column of innermost code blocks is greater than 4.

 

Simple If Statement

Col 0-3       Col 4-7

1101 - J       0000

0110 - E      0000

0001 - D      0000

…               …

XXXX           1000

 

Loop Statement

 

XXXX           1000

…               …

1100 - X      0000

1101 - J       0000

0110 - E      0000

0000 - U      0000

 

If-Elseif-Else Statement

 

1101 - J       0000

0110 - E      0000

0001 - D      0000

…               …               if block

0011 - N

0110 - E      0000

0001 - D      0000

XXXX           1000

…               …

1101 - J       0000

0110 - E      0000

0001 - D      0000

…               …               elseif block

0011 - N

0110 - E      0000

0001 - D      0000

XXXX           1000

…               …               else block

1110 - K      0000

0010 - P      0100