DSPIC30F4011-30I/P Microchip Technology Inc., DSPIC30F4011-30I/P Datasheet - Page 32

• Manufacturer Part Number: DSPIC30F4011-30I/P
• Description: 16 BIT MCU/DSP 40LD 30MIPS 48 KB FLASH
• Manufacturer: Microchip Technology Inc.
• Type: DSPr

Specifications of DSPIC30F4011-30I/P

• A/d Inputs: 9-Channels, 10-Bit
• Comparators: 4
• Cpu Speed: 30 MIPS
• Eeprom Memory: 1K Bytes
• Input Output: 30
• Interface: CAN, I2C/SPI/UART, USART
• Ios: 30
• Memory Type: Flash
• Number Of Bits: 16
• Package Type: 40-pin PDIP
• Programmable Memory: 48K Bytes
• Ram Size: 2K Bytes
• Timers: 5-16-bit, 2-32-bit
• Voltage, Range: 2.5-5.5
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

dsPIC30F
3.
2.5.2.2
The MAC class of instructions (with the exception of
MPY, MPY.N, ED and EDAC) can optionally write a
rounded version of the high word (bits 31 through 16)
of the accumulator that is not targeted by the instruction
into data space memory. The write is performed across
the X bus into combined X and Y address space. The
following addressing modes are supported:
1.
2.
2.5.2.3
The round logic is a combinational block, which per-
forms a conventional (biased) or convergent (unbiased)
round function during an accumulator write (store). The
Round mode is determined by the state of the RND bit
in the CORCON register. It generates a 16-bit, 1.15 data
value which is passed to the data space write saturation
logic. If rounding is not indicated by the instruction, a
truncated 1.15 data value is stored and the LS Word is
simply discarded.
Conventional rounding takes bit 15 of the accumulator,
zero-extends it and adds it to the ACCxH word (bits 16
through 31 of the accumulator). If the ACCxL word (bits
0 through 15 of the accumulator) is between 0x8000
and 0xFFFF (0x8000 included), ACCxH is incre-
mented. If ACCxL is between 0x0000 and 0x7FFF,
ACCxH is left unchanged. A consequence of this algo-
rithm is that over a succession of random rounding
operations, the value will tend to be biased slightly
positive.
Convergent (or unbiased) rounding operates in the
same manner as conventional rounding, except when
ACCxL equals 0x8000. If this is the case, the LS bit (bit
16 of the accumulator) of ACCxH is examined. If it is ‘1’,
ACCxH is incremented. If it is ‘0’, ACCxH is not modi-
fied. Assuming that bit 16 is effectively random in
nature, this scheme will remove any rounding bias that
may accumulate.
DS70082G-page 30
Bit 39 Catastrophic Overflow
The bit 39 overflow status bit from the adder is
used to set the SA or SB bit, which remain set
until cleared by the user. No saturation operation
is performed and the accumulator is allowed to
overflow (destroying its sign). If the COVTE bit in
the INTCON1 register is set, a catastrophic
overflow can initiate a trap exception.
W13, Register Direct:
The rounded contents of the non-target accumula-
tor are written into W13 as a 1.15 fraction.
[W13]+=2, Register Indirect with Post-Increment:
The rounded contents of the non-target accumu-
lator are written into the address pointed to by
W13 as a 1.15 fraction. W13 is then
incremented by 2 (for a word write).
Accumulator ‘Write Back’
Round Logic
Preliminary
The SAC and SAC.R instructions store either a trun-
cated (SAC) or rounded (SAC.R) version of the contents
of the target accumulator to data memory, via the X bus
(subject to data saturation, see Section 2.5.2.4). Note
that for the MAC class of instructions, the accumulator
write back operation will function in the same manner,
addressing combined MCU (X and Y) data space
though the X bus. For this class of instructions, the data
is always subject to rounding.
2.5.2.4
In addition to adder/subtractor saturation, writes to data
space may 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 are
combined and used to select the appropriate 1.15 frac-
tional 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 written to memory is forced to the
maximum positive 1.15 value, 0x7FFF. For input data
less than 0xFF8000, data written to memory is forced
to the maximum negative 1.15 value, 0x8000. The MS
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.
2.5.3
The barrel shifter is capable of performing up to 15-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 accumulators 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 will shift the operand
right. A negative value will shift the operand left. A
value of ‘0’ will 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 to
31 for right shifts, and bit positions 0 to 15 for left shifts.
BARREL SHIFTER
Data Space Write Saturation
 2004 Microchip Technology Inc.