A96G140/A96G148/A96A148 User’s manual
4. Central processing unit ABOV
33
External data memory: Data can be moved between the accumulator and the external memory
location in one of two addressing modes. In 8-bit addressing mode, the external location is
addressed by either R0 or R1; in 16-bit addressing mode, the location is addressed by the
DPTR.
Unconditional Jumps: Four sorts of unconditional jump instructions are available.
—
Short jumps (SJMP) are relative jumps (limited from -128bytes to +127bytes).
—
Long jumps (LJMP) are absolute 16-bit jumps.
—
Absolute jumps (AJMP) are absolute 11-bit jumps (ex. within a 2Kbyte memory page).
—
Indexed jump,
JMP @A+DPTR
. This instruction jumps to a location of which address is
stored in DPTR register and offset by a value stored in the accumulator.
Subroutine calls and returns: There are only two sorts of subroutine call, ACALL and LCALL,
which are Absolute and Long. Two return instructions are provided, RET and RETI. The latter
is for interrupt service routines.
Conditional jumps: All conditional jump instructions use relative addressing, so they are limited
to the range of -128bytes to +127bytes.
Boolean instructions: The bit-addressable registers in both direct and SFR space may be
manipulated using Boolean instructions. Logical functions are available which use the carry
flag and an addressable bit as operands. Each addressable bit can be set, cleared or tested
in a jump instruction.
Flag: Certain instructions affect one or more flags that are generated by ALU.
