Branch

Instruction Name	Branch
Mnemonics	B/BC/BOV/BPL BEQ/BLT/BLE/BUSC NOPP/BNC/BNOV/BMI BNEQ/BGE/BGT/BESC BEXT
CP1610 Clock Cycles	7 or 9
Interruptible	Yes
Opcode Range	$0200-$023F

Similar to the Jump family of instructions, Branch is also an entire family of instructions that are represented as any of several different possible mnemonics, depending on the flags indicated in the opcode. The opcode format breaks down as follows.

   Format - Decle #1
   0000:0010:00de:nccc  0000:00aa

   where:

       d      indicates the direction of the branch
              such that:
                  d == 0    indicates to branch in the forward direction
                  d == 1    indicates to branch in the reverse direction

       e      indicates to branch on an external condition
              such that if e == 0, then:
                  nccc == 0000   branch unconditionally (B)
                  nccc == 0001   branch if Carry Flag is set (BC)
                  nccc == 0010   branch if Overflow Flag is set (BOV)
                  nccc == 0011   branch if Sign Flag is clear (BPL)
                  nccc == 0100   branch if Zero Flag is set (BEQ or BZ)
                  nccc == 0101   branch if Sign Flag != Overflow Flag (BLT)
                  nccc == 0110   branch if either Zero Flag is set
                                 or if Sign Flag != Overflow Flag (BLE)
                  nccc == 0111   branch if Sign Flag != Carry Flag (BUSC)
                  nccc == 1000   do not branch unconditionally (NOPP)
                  nccc == 1001   do not branch if Carry Flag is set (BNC)
                  nccc == 1010   do not branch if Overflow Flag is set (BNOV)
                  nccc == 1011   do not branch if Sign Flag is clear (BMI)
                  nccc == 1100   do not branch if Zero Flag is set (BNEQ or BNZ)
                  nccc == 1101   do not branch if Sign Flag != Overflow Flag (BGE)
                  nccc == 1110   do not branch if either Zero Flag is set
                                 or if Sign Flag != Overflow Flag (BGT)
                  nccc == 1111   do not branch if Sign Flag != Carry Flag (BESC)
              otherwise if e == 1, then:
                  nccc    branch if this value matches the pins EBCA0-EBCA3 (BEXT)

The Branch opcode family is often represented as many different mnemonics, to make life a little easier for the programmer. The mnemonic used to represent this opcode depends on the combination of the e, n, and ccc parameters mentioned above, according to the following chart.

Mnemonics To Parameters

Mnemonic	e	n	ccc
B	0	0	000
BC	0	0	001
BOV	0	0	010
BPL	0	0	011
BEQ or BZ	0	0	100
BLT	0	0	101
BLE	0	0	110
BUSC	0	0	111
NOPP	0	1	000
BNC	0	1	001
BNOV	0	1	010
BMI	0	1	011
BNEQ or BZ	0	1	100
BGE	0	1	101
BGT	0	1	110
BESC	0	1	111
BEXT	1	any value