Data Sheet
March 2000
DSP1627 Digital Signal Processor
38
Lucent Technologies Inc.
5 Software Architecture
(continued)
Special Function Instructions
All forms of the special function require one word of program memory and execute in one instruction cycle. (If PC
points to external memory, add programmed wait-states.)
aD = aS
—
Load destination accumulator from source accumulator
aD = –aS
—
2's complement
aD = ~aS
*
—
1's complement
aD = rnd(aS)
—
Round upper 20 bits of accumulator
aDh = aSh + 1 —
Increment upper half of accumulator (lower half cleared)
aD = aS + 1
—
Increment accumulator
aD = y
—
Load accumulator with 32-bit y register value with sign extend
aD = p
—
Load accumulator with 32-bit p register value with sign extend
The above special functions can be conditionally executed, as in:
if CON instruction
and with an event counter
ifc CON instruction
which means:
if CON is true then
c1 = c1 + 1
instruction
c2 = c1
else
c1 = c1 + 1
The above special function statements can be executed unconditionally by writing them directly, e.g., a0 = a1.
aD = aS >> 1
aD = aS >> 4
aD = aS >> 8
aD = aS >> 16
}
Arithmetic right shift (sign preserved) of 36-bit accumulators
*
This function is not available for the DSP16A.
aD = aS << 1
aD = aS << 4
aD = aS << 8
aD = aS << 16
}
Arithmetic left shift (sign not preserved) of the lower 32 bits of accumulators
(upper 4 bits are sign-bit-extended from bit 31 at the completion of the shift)
Table 15. Replacement Table for Special Function Instructions
Replace
aD
aS
CON
Value
a0, a1
Meaning
One of two DAU accumulators.
mi, pl, eq, ne, gt, le, lvs, lvc, mvs, mvc, c0ge,
c0lt, c1ge, c1lt, heads, tails, true, false, allt, allf,
somet, somef, oddp, evenp, mns1, nmns1, npint,
njint, lock
See Table 17 for definitions of mnemonics.