| Octal Order Code | Nmenonic | Execution |
|---|---|---|
| 060 | BUX X N | Branch on Unit Indexing This instruction treats the contents of the accummulator X as an index word, adding 1 to bits 9 to 23, subtracting 1 from bits 0 to 8, and then branching to N unless the new value of the count is zero. There is no carry between bits 9 to 23 and bits 0 to 9 (or vice versa). The maximum value of the modifier is 32,767 and of the counter 511. An initial count of zero is effectively equivalent to 512. C is not used and will be left clear. V is not used and remains unchanged. Modification The BUX statement has no M field. |
| 062 | BDX X N | Branch on Double Indexing This instruction treats the contents of the accummulator X as an index word, adding 2 to bits 9 to 23, subtracting 1 from bits 0 to 8, and then branching to N unless the new value of the count is zero. There is no carry between bits 9 to 23 and bits 0 to 9 (or vice versa). The maximum value of the modifier is 32,767 and of the counter 511. An initial count of zero is effectively equivalent to 512. C is not used and will be left clear. V is not used and remains unchanged. Modification The BDX statement has no M field. |
| 064 | BCHX X N | Branch on Character Indexing The BCHX instruction operates on a character index word. The character index word is held in the specified accumulator and is notionally divided into three parts, bits 0 to 1, bits 2 to 8 and bits 9 to 23. In bits 2 to 8 there is a count. The BCHX instruction subtracts 1 from bits 2 to 8 (the count) and adds 1 to bits 0 to 1. When bits 0 to 1 contain 3 and a further 1 is added, then there is a circular carry so that bits 0 to 1 become zero and 1 is added to bits 9 to 23. The BCHX causes a branch to the address specified in N if the count in bits 2 to 8 is not zero after 1 has been subtracted from it. If however, the count has become zero then then next instruction in sequence is obeyed. The maximum count which may be held in bits 2 to 8 is 127. If the count is initially zero this will effectively be equivalent to a count of 128. C is not used and will be left clear. V is not used and remains unchanged. Modification The BCHX statement has no M field. |
| 066 | BCT X N | Branch on Count The BCT instruction subtracts 1 from the least significant 15 bits of the specified accumulator. It then transfers control to the program location specified by N, unless B9 to B23 of X has been reduced to zero, in which case control passes to the next instruction in sequence. The most 9 significant bits of X are unchanged. C is not used and will be left clear. V is not used and remains unchanged. Modification The BCT statement has no M field. |