~ National ~ Semiconductor - Al Kossow's Bitsavers

6.0 Instruction Set Reference (Continued)
LCALL Conditional Long Call
Syntax
LCALL Rs, p, s, nn -register, absolute
Affected Flags
None
Description
If the bit in position p of register Rs is equal to the bit s, then
push the Program Counter, the ALU flags, the Global Interrupt
Enable bit [GIE], and the current register bank selections
onto the internal Address Stack. Following the push,
transfer control to the instruction at the absolute memory
address nn. 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
Call the "Load.Xmit" subroutine when the Transmitter FIFO
Empty flag, [TFE], of the Network Command Flag register
(NCF) is "1".
EXX 0,0
LCALL NCF,7,1, Load.Xmit
Instruction Format
1 10 10 I 0 11 11 11 I 1
1
. Opcode .s. p
15 8 7
1 L
15
T-states
(2 + 2)
Bus Timing
Figure 9
Operation
;select main A, alt B
;If [TFE] = 1 call
If Rs[p] = s then
PC & [GIE] & ALU flags & register bank selections
- Address Stack
nn-PC
End if
4
Rs
o
o
LCALL Unconditional Long Call
Syntax
LCALL
nn
Affected Flags
None
Description
-absolute
Pushes the Program Counter, the ALU flags, the Global Interrupt
Enable bit [GIE], and the current register bank selections
onto the internal Address Stack; then unconditionally
transfers control to the instruction at the absolute memory
address nn. The value of nn is 16 bits long, (range: 0 to
64k), therefore, all of instruction memory can be addressed.
Example
Transfer control to the subroutine "Send.it.all", which could
be located anywhere in instruction memory.
LCALL
Send.it.all
Instruction Format
111110101111111011101010101010101
Opcode
15
15
T-states
(2 + 2)
Bus Timing
Figure 9
Operation
PC & [GIE] & ALU flags & register bank selections
- Address Stack
nn-PC
nn
o
o
2-112