DSPIC33FJ32MC202 Microchip Technology Inc., DSPIC33FJ32MC202 Datasheet - Page 26

• Manufacturer Part Number: DSPIC33FJ32MC202
• Description: High-performance, 16-bit Digital Signal Controllers
• Manufacturer: Microchip Technology Inc.

2.6.3.2
In addition to adder/subtracter saturation, writes to data
space can also be saturated, but without affecting the
contents of the source accumulator. The data space
write saturation logic block accepts a 16-bit, 1.15 frac-
tional value from the round logic block as its input,
together with overflow status from the original source
(accumulator) and the 16-bit round adder. These inputs
are combined and used to select the appropriate 1.15
fractional value as output to write to data space
memory.
If the SATDW bit in the CORCON register is set, data
(after rounding or truncation) is tested for overflow and
adjusted accordingly:
• For input data greater than 0x007FFF, data writ-
• For input data less than 0xFF8000, data written to
The Most Significant bit of the source (bit 39) is used to
determine the sign of the operand being tested.
If the SATDW bit in the CORCON register is not set, the
input data is always passed through unmodified under
all conditions.
DS70283B-page 24
ten to memory is forced to the maximum positive
1.15 value, 0x7FFF.
memory is forced to the maximum negative 1.15
value, 0x8000.
Data Space Write Saturation
Preliminary
2.6.4
The barrel shifter can perform up to 16-bit arithmetic or
logic right shifts, or up to 16-bit left shifts in a single
cycle. The source can be either of the two DSP accu-
mulators or the X bus (to support multi-bit shifts of
register or memory data).
The shifter requires a signed binary value to determine
both the magnitude (number of bits) and direction of the
shift operation. A positive value shifts the operand right.
A negative value shifts the operand left. A value of ‘0’
does not modify the operand.
The barrel shifter is 40 bits wide, thereby obtaining a
40-bit result for DSP shift operations and a 16-bit result
for MCU shift operations. Data from the X bus is pre-
sented to the barrel shifter between bit positions 16 and
31 for right shifts, and between bit positions 0 and 16
for left shifts.
BARREL SHIFTER
© 2007 Microchip Technology Inc.