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Mnemonic
TIJMP
TABLE INDIRECT JUMP. Causes execution
to continue at an address selected from a
table of addresses.
The TIJMP instruction reduces the interrupt
response time associated with servicing
multiple interrupt sources that are multiplexed
into a single interrupt request line (a single
vector). It is typically used in conjunction with
the EPAIPV register to determine the source
of multiplexed EPA interrupts. ("Servicing the
Multiplexed EPA Interrupt with Software" on
page 10-29 discusses the use of TIJMP with
the EPA.)
The first word register, TBASE, contains the
16-bit address of the beginning of the jump
table. TBASE can be located in RAM up to
0FEH without windowing or above 0FFH with
windowing. The jump table itself can be
placed at any nonreserved memory location
on a word boundary.
The second word register, INDEX, contains
the 16-bit address that points to a register
containing a 7-bit value. This value is used to
calculate the offset into the jump table. Like
TBASE, INDEX can be located in RAM up to
0FEH without windowing or above 0FFH with
windowing. Note that the 16-bit address
contained in INDEX is absolute; it disregards
any windowing that may be in effect when the
TIJMP instruction is executed.
The byte operand, #MASK, is 7-bit immediate
data to mask INDEX. #MASK is ANDed with
INDEX to determine the offset (OFFSET).
OFFSET is multiplied by two, then added to
the base address (TBASE) to determine the
destination address (DEST X).
[INDEX] AND #MASK = OFFSET
(2 × OFFSET) + TBASE = DEST X
←
PC
(DEST X)
Z
—
Table A-6. Instruction Set (Continued)
Operation
PSW Flag Settings
N
C
V
VT
ST
—
—
—
—
—
INSTRUCTION SET REFERENCE
Instruction Format
TIJMP
TBASE, [INDEX], #MASK
(11100010) [INDEX] (#MASK) (TBASE)
NOTE: TIJMP multiplies OFFSET by two
to provide for word alignment of
the jump table. This must be con-
sidered
when
EPAIPV register and when set-
ting up the jump table.
decoding
the
A-39
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