~ National ~ Semiconductor - Al Kossow's Bitsavers

6.0 Instruction Set Reference (Continued)
WMP Conditional Long Jump
Syntax
LJMP Rs, p, s, nn -register, absolute
Affected Flags
None
Description
Conditionally transfers control to the instruction at the absolute
memory address nn if the bit in position p of register Rs
is equal to the state of the bit s. The operand Rs may specify
any active CPU register. The value of p may be from 0 to
7, where 0 corresponds to the LSB of Rs and 7 corresponds
to the MSB of Rs. The absolute value nn is 16 bits long,
(range: 0 to 64k), therefore, all of instruction memory can be
addressed.
Example
Long Jump to one of the receiver error handling routines
based on the contents of the Error Code Register (ECR}.
EXX 0,1,3, ;select main A, alt B
OR 01000000B,TSR
; and clear [GIE]
;set [SEC] in (TSR}
MOVE ECR, R11
;read (ECR}
; Determine error condition
LJMP R11, 0,1, Software_error
LJMP R11, 1, 1, Loss_of_Midbit
LJMP R11, 2,1, InvaliLEndinQ-Seq
LJMP R11, 3, 1, Parity_error
LJMP R11, 4,1, Software_error
Instruction Format
15
15
T-states
(2 + 2)
Bus Timing
Figure 9
Operation
If Rs[p] = s
then nn-+ PC
B 7
1
nn
p
4
1
I I
Rs
o
o
WMP Unconditional Long Jump
Syntax
LJMP nn -absolute
LJMP Dr] -indexed
Affected Flags
None
Description
Unconditionally transfers control to the instruction at the
memory address specified by the operand. The operand
may either specify an absolute instruction address nn, (16
bits long), or an index register Ir, which contains an instruction
address. LJMP's addressing range is from 0 to 64k;
(I.e., all of instruction memory can be addressed).
Example
Transfer control to the instruction labeled "Reset.System",
which may be located anywhere in instruction memory.
LJMP Reset.System ; go reset the system
Instruction Format
LJMP nn
1 11110101111111010101010101010101
. Opcode .
15 0
1 nn 1
15 o
LJMP
Dr]
1111101~~~0~~1011101Ir 10101010101
15 6,J, 4 0
OO-IW
01-IX
10-IY
11-IZ
T-states
LJMP nn -(2 + 2)
LJMP Dr] -2
Bus Timing
LJMP nn -Figure 9
LJMP Dr] -Figure 9
Operation
LJMP nn
nn-+PC
LJMP Dr]
Ir-+PC
2-113