MA330026 Microchip Technology, MA330026 Datasheet - Page 34

• Manufacturer Part Number: MA330026
• Description: Daughter Cards & OEM Boards dsPIC33FJ16MC102 Plug-In Module
• Manufacturer: Microchip Technology

Specifications of MA330026

• Rohs: yes
• Product: Plug-In Modules
• Core: PIC
• Data Bus Width: 16 bit
• Description/function: dsPIC33F MC 28 Pin QFN to 100 Pin Plug-in-Module
• Interface Type: I2C, SPI, UART
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Operating Supply Voltage: 3 V to 3.6 V
• For Use With: DM330021, DM330022, DM330023

dsPIC33FJ16GP101/102 AND dsPIC33FJ16MC101/102
The SA and SB bits are modified each time data
passes through the adder/subtracter, but can only be
cleared by the user application. When set, they indicate
that the accumulator has overflowed its maximum
range (bit 31 for 32-bit saturation or bit 39 for 40-bit
saturation) and will be saturated (if saturation is
enabled). When saturation is not enabled, SA and SB
default to bit 39 overflow, and therefore, indicate that a
catastrophic overflow has occurred. If the COVTE bit in
the INTCON1 register is set, the SA and SB bits will
generate an arithmetic warning trap when saturation is
disabled.
The Overflow and Saturation Status bits can optionally
be viewed in the STATUS Register (SR) as the logical
OR of OA and OB (in bit OAB) and the logical OR of SA
and SB (in bit SAB). Programmers can check one bit in
the STATUS register to determine whether either
accumulator has overflowed, or one bit to determine
whether either accumulator has saturated. This is
useful for complex number arithmetic, which typically
uses both accumulators.
The device supports three Saturation and Overflow
modes:
• Bit 39 Overflow and Saturation:
• Bit 31 Overflow and Saturation:
• Bit 39 Catastrophic Overflow:
DS70652C-page 34
When bit 39 overflow and saturation occurs, the
saturation logic loads the maximally positive 9.31
value (0x7FFFFFFFFF) or maximally negative 9.31
value (0x8000000000) into the target accumulator.
The SA or SB bit is set and remains set until
cleared by the user application. This condition is
referred to as ‘super saturation’ and provides pro-
tection against erroneous data or unexpected
algorithm problems (such as gain calculations).
When bit 31 overflow and saturation occurs, the
saturation logic then loads the maximally positive
1.31 value (0x007FFFFFFF) or maximally nega-
tive 1.31 value (0x0080000000) into the target
accumulator. The SA or SB bit is set and remains
set until cleared by the user application. When
this Saturation mode is in effect, the guard bits are
not used, so the OA, OB or OAB bits are never
set.
The bit 39 Overflow Status bit from the adder is
used to set the SA or SB bit, which remains set
until cleared by the user application. 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.
Preliminary
3.6.3
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 which is not targeted by the instruc-
tion 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:
• W13, Register Direct:
• [W13] + = 2, Register Indirect with Post-Increment:
The rounded contents of the non-target
accumulator are written into W13 as a
1.15 fraction.
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’
© 2011 Microchip Technology Inc.