ACCUMULATE
LOADCONST
NEGATE
Description
Function
1
X
0
Adds the current
result to the previous
accumulate result.
Accumulation
1
X
1
This function takes
the current result,
converts it into two’s
complement, and adds
it to the previous
result.
Decimation
Systolic Registers
There are two systolic registers per variable precision DSP block. If the variable precision DSP block is not
configured in systolic FIR mode, both systolic registers are bypassed.
The first set of systolic registers consists of 18-bit and 19-bit registers that are used to register the 18-bit and
19-bit inputs of the upper multiplier, respectively.
The second set of systolic registers are used to delay the chainout output to the next variable precision DSP
block.
You must clock all the systolic registers with the same clock source as the output register bank.
Double Accumulation Register
The double accumulation register is an extra register in the feedback path of the accumulator. Enabling the
double accumulation register will cause an extra clock cycle delay in the feedback path of the accumulator.
This register has the same
CLK
,
ENA
, and
ACLR
settings as the output register bank.
By enabling this register, you can have two accumulator channels using the same number of variable precision
DSP block.
Output Register Bank
The positive edge of the clock signal triggers the 64-bit bypassable output register bank and is cleared after
power up.
The following variable precision DSP block signals control the output register per variable precision DSP
block:
•
CLK[2..0]
•
ENA[2..0]
•
ACLR[1]
Operational Mode Descriptions
This section describes how you can configure an Cyclone V variable precision DSP block to efficiently
support the following operational modes:
• Independent Multiplier Mode
Variable Precision DSP Blocks in Cyclone V Devices
Altera Corporation
CV-52003
Systolic Registers
3-10
2014.01.10