Echelon Neuron - Manual (Page 84)

BRNEQ (Branch If Not Equal)
The BRNEQ instruction compares TOS with a specified number and performs a
conditional branch if they are not equal. The BRNEQ instruction uses the
relative addressing mode for the branch destination and the immediate
addressing mode for the test condition. The BRNEQ instruction compares TOS
to a constant expression. The expression number must resolve at link time to a
constant in the range -128 to +127.
After the comparison, the BRNEQ instruction branches forward or backward
with a signed relative displacement of -125 to +130 bytes if TOS is not equal to
number; otherwise, program operation continues with the next instruction. The
displacement expression must resolve at link time to a value in the range -128 to
+127 (three less than the actual displacement because the displacement
calculation includes the size of the BRNEQ operation itself).
The Neuron Assembler also supports the use of a label for the displacement
expression; manual calculation of the displacement value is not required.
The BRNEQ instruction applies to Series 3100, 5000, and 6000 devices.
Syntax:
The BRNEQ instruction requires two operands: one to specify the number for
comparison and one to specify the displacement or label:
BRNEQ #number, displacement
BRNEQ #number, label
The number sign or hash (#) is required to specify the immediate value.
Table 20 describes the attributes of the BRNEQ instruction.
Table 20. BRNEQ Instruction
Instruction Hexadecimal
Opcode
Instruction
Size (Bytes)
CPU Cycles
Required
Affect on
Carry Flag
BRNEQ 76 3 4
(if branch is
taken)
6
(if branch is not
taken)
None
Example:
The following example tests the argument in TOS for the ASCII codes 65 (for ‘A’),
66 (for ‘B’), and 67 (for ‘C’), and calls a related function for each. The example
shows one possible assembly implementation of a C-language switch/case
construct.
Example APEXP ; (argument -- )
74 Neuron Assembly Language Instruction Statements