INSTRUCTION DESCRIPTIONS
MOTOROLA
INSTRUCTION SET DETAILS A - 123
specified in the effective address field is always updated independently of the state of the
n
th
bit. All address register indirect addressing modes may be used to reference the
source operand S. Absolute short and I/O short addressing modes may also be used.
Restrictions:
A JSCLR instruction used
within a DO loop
cannot specify the
loop
address
(LA) as its target.
A JSCLR located at LA, LA–1, or LA–2 of a DO loop, cannot specify the program control-
ler registers SR, SP, SSH, SSL, LA, or LC as its target.
JSCLR SSH or JSCLR SSL cannot
follow
an instruction that changes the SP.
A JSCLR instruction cannot be repeated using the REP instruction.
Example:
:
JSCLR #$1,Y:<<$FFE3,$1357 ;go sub. at P:$1357 if bit 1 in Y:$FFE3 is clear
:
Explanation of Example:
In this example, program execution is transferred to the sub-
routine at absolute address P:$1357 in program memory if bit 1 of the external I/O loca-
tion Y:<<$FFE3 is a zero. If the specified bit is not clear, no jump is taken and the
program counter (PC) is incremented by 1.
JSCLR Jump to Subroutine if Bit Clear JSCLR