PDSP16116 Datasheet, PDF (10/18 Pages) Mitel Networks Corporation – 16 X 16 Bit Complex Multiplier

PDSP16116/A/MC
SOBFP (BFP MODE ONLY)
Start of BFP: This input should be held low for the first cycle
of the first pass of the BFP calculations (see Fig.7). It serves
to reset the internal registers associated with BFP control.
When operating in normal mode this input should be tied low.
EOPSS (BFP MODE ONLY)
End of pass: This input should be held low for the last cycle
of each pass and for the lay time between passes. It instructs
the control logic to update the value of the global weighting
register and prepare the BFP circuitry for the next pass. When
operating in normal mode this input should be tied low.
AR15:13 (BFP MODE ONLY)
Three Msbs of the real part of the A-word : These are used
in the FFT butterfly application to deteremine the magnitude of
the real part of the A-word and, hence, to determine if there will
be any chage of word growth in the PDSP16318 Complex
Accumulator. When operating in normal mode, these inputs
are not used and may be tied low.
AI15:13 (BFP MODE ONLY)
Three Msbs of the imaginary part of the A-word : used in
the same fashion as AR.
SFTR2:0 (BFP MODE ONLY)
Accumulator result shift control. These pins should be
linked directly to the S2:0 pins on the PDSP16318 Complex
Accumulator. They control the accumulator’s barrel shifter
(see Table 5). The purpose of this shift is to minimise sign
extension in the multiplier or accumulator ALU’s. When
operating in normal mode, these output are superfluous.
SFTR2:0
FUNCTION
000
001
010
011
100
101
110
111
Reserved
Reserved
Reserved
Shift right by one
No shift
Shift left by one
Shift left by two
Reserved
Table 5 - Auccumulator Shifts ( BFP mode )
GWR4:0 (BFP MODE ONLY)
Contents of the global weighting register: This stores the
weighting of the largest word present with respect to the
weighting of the original input words. Hence, if the contents of
the GWR are 00010, this indicates that the largest word
currently being processed has its binary point two bits to the
right of the original data at the start of the BFP calculations.
The contents of this register are updated at the end of each
pass, according to the largest value of WTOUT occuring
during that pass. (i.e. If WTOUT = 11, then GWR will be
increased by 2). The GWR is presented in two’s complement
format. These outputs are superfluous in normal mode.
WTOUT1:0 (BFP MODE ONLY)
Word tag output. This tag records the weighting of the
output words from the current cycle relative to the current
global weighting register (see Table 6). It should be stored
along with the A’ and B’ words as it will form the input word
tags, WTA and WTB, for each complex word during the next
pass. These outputs are superfluous in normal mode.
WTOUT1:0
00
01
10
11
Weighting of the output relative to
the current global weighting register
One less
The same
One more
Two more
Table 6 - Word Tag Weightings
WTA1:0 (BFP MODE ONLY)
Word tag from the A-word. This word records the
weighting of the A-word relative to the global weighting
register on the previous pass. Although the A-word inself is
not processed in the PDSP16116, this information is required
by the control logic for the radix-2 butterfly FFT application.
These inputs should be tied low in normal mode.
WTB1:0 (BFP & NORMAL MODES)
In BFP mode, this is the word tag from the B-word. This is
operated in the same manner as WTA but for the B-word. The
value of the word tags are used to ensure that the binary
weighting of the A word and the product of the complex
multiplier are the same at the inputs to the complex
accumulator. Depending on which word is the larger, the
weighting adjustment is performed using either the internal
shifter or an external shifter controlled by SFTA. The word
tags are also used to maintain the weighting of the final result
to within plus two and minus one binary points relative to the
new GWR. (On the first pass all word tags will be ignored).
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