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This document provides a summary of the extended mnemonic opcodes for branch instructions. This program may serve as a tutorial for programmers that are new to 370 assembler or as a reference for experienced programmers. In the following tables the leftmost three columns show the mnemonic with the operands and a brief description. The rightmost three columns show the instruction format, the actual mnemonic opcode and the mask and addressing format that is generated from the extended mnemonic.
Notes: D2=displacement, X2=index register, B2=base register, R2=register containing branch address
The following mnemonic opcodes are used for an Unconditional Branch or No Branch.
| Mnemonic | Operands | Description | Format | Opcode | Mask/Operands |
| B | D2(X2,B2) | Unconditional Branch | RX | BC | 15,D2(X2,B2) |
| BR | R2 | RR | BCR | 15,R2 | |
| NOP | D2(X2,B2) | No Operation | RX | BC | 0,D2(X2,B2) |
| NOPR | R2 | RR | BCR | 0,R2 |
The following mnemonic opcodes are used after Compare Instructions.
| Mnemonic | Operands | Description | Format | Opcode | Mask/Operands |
| BH | D2(X2,B2) | Branch on High | RX | BC | 2,D2(X2,B2) |
| BHR | R2 | RR | BCR | 2,R2 | |
| BL | D2(X2,B2) | Branch on Low | RX | BC | 4,D2(X2,B2) |
| BLR | R2 | RR | BCR | 4,R2 | |
| BE | D2(X2,B2) | Branch on Equal | RX | BC | 8,D2(X2,B2) |
| BER | R2 | RR | BCR | 8,R2 | |
| BNH | D2(X2,B2) | Branch on Not High | RX | BC | 13,D2(X2,B2) |
| BNHR | R2 | RR | BCR | 13,R2 | |
| BNL | D2(X2,B2) | Branch on Not Low | RX | BC | 11,D2(X2,B2) |
| BNLR | R2 | RR | BCR | 11,R2 | |
| BNE | D2(X2,B2) | Branch on Not Equal | RX | BC | 7,D2(X2,B2) |
| BNER | R2 | RR | BCR | 7,R2 |
The following mnemonic opcodes are used after Arithmetic Instructions.
| Mnemonic | Operands | Description | Format | Opcode | Mask/Operands |
| BP | D2(X2,B2) | Branch on Plus | RX | BC | 2,D2(X2,B2) |
| BPR | R2 | RR | BCR | 2,R2 | |
| BM | D2(X2,B2) | Branch on Minus | RX | BC | 4,D2(X2,B2) |
| BMR | R2 | RR | BCR | 4,R2 | |
| BZ | D2(X2,B2) | Branch on Zero | RX | BC | 8,D2(X2,B2) |
| BZR | R2 | RR | BCR | 8,R2 | |
| BO | D2(X2,B2) | Branch on Overflow | RX | BC | 1,D2(X2,B2) |
| BOR | R2 | RR | BCR | 1,R2 | |
| BNP | D2(X2,B2) | Branch on Not Plus | RX | BC | 13,D2(X2,B2) |
| BNPR | R2 | RR | BCR | 13,R2 | |
| BNM | D2(X2,B2) | Branch on Not Minus | RX | BC | 11,D2(X2,B2) |
| BNMR | R2 | RR | BCR | 11,R2 | |
| BNZ | D2(X2,B2) | Branch on Not Zero | RX | BC | 7,D2(X2,B2) |
| BNZR | R2 | RR | BCR | 7,R2 | |
| BNO | D2(X2,B2) | Branch on No Overflow | RX | BC | 14,D2(X2,B2) |
| BNOR | R2 | RR | BCR | 14,R2 |
The following mnemonic opcodes are used after Test Under Mask Instructions.
| Mnemonic | Operands | Description | Format | Opcode | Mask/Operands |
| BO | D2(X2,B2) | Branch if Ones | RX | BC | 1,D2(X2,B2) |
| BOR | R2 | RR | BCR | 1,R2 | |
| BM | D2(X2,B2) | Branch if Mixed | RX | BC | 4,D2(X2,B2) |
| BMR | R2 | RR | BCR | 4,R2 | |
| BZ | D2(X2,B2) | Branch if Zero | RX | BC | 8,D2(X2,B2) |
| BZR | R2 | RR | BCR | 8,R2 | |
| BNO | D2(X2,B2) | Branch if Not Ones | RX | BC | 14,D2(X2,B2) |
| BNOR | R2 | RR | BCR | 14,R2 | |
| BNM | D2(X2,B2) | Branch if Not Mixed | RX | BC | 11,D2(X2,B2) |
| BNMR | R2 | RR | BCR | 11,R2 | |
| BNZ | D2(X2,B2) | Branch if Not Zero | RX | BC | 7,D2(X2,B2) |
| BNZR | R2 | RR | BCR | 7,R2 |
The purpose of this document is to assist as a tutorial for new programmers or as a quick reference for experienced programmers. These reference documents are made available on an "as-is" basis and may be downloaded, copied and modified for specific situations as long as the copyright information is not removed or changed. As always, it is the programmer's responsibility to thoroughly test all programs and review all documentation.
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