AN2072 Freescale Semiconductor / Motorola, AN2072 Datasheet - Page 21

• Manufacturer Part Number: AN2072
• Description: AN2072, Decision Feedback Equalizer for StarCore-Based DSPs
• Manufacturer: Freescale Semiconductor / Motorola

LOOP 2
Freescale Semiconductor
;End loop_compute
;****End loop_address_setting
1.
The v matrix is arranged in Matlab as shown in Equation 26 (for our example with, an optimum delay = 8
and chan_mem = 4).
In this part of the algorithm, data is read from two different locations in memory:
— “v” (starting at the location of the last entry in v)
— “channel_h” (starting at the first element of the impulse response)
During the execution of LOOP 2 (following the same notation as the Matlab routine) data is read out as
shown in Table 2. Note that the number of elements read in each iteration depends on the
min(chan_mem, jj)+1, where jj is decremented by one from a value of N
However, in the DSP code this process is done slightly different. Data is arranged in the v array in the
DSP as shown in Equation 27. As the algorithm progresses, data is read out every iteration as shown
in Table 3.
asrr d2,d6
asrr #2,d6
moves.2f d6:d7,(r1)+
loopend1
add #1,d8
tfra BASE_ROW,r0;
loopend0
First
Second
Third
Fourth
Fifth
Sixth
Seventh
Eighth
Iteration
Decision Feedback Equalizer for StarCore™-Based DSPs, Rev. 1
V
=
V
=
0 0 0 0 v 1 ( ) v 2 ( ) v 3 ( ) v 4 ( ) v 5 ( ) v 6 ( ) v 7 ( ) v 8 ( )
asrr d2,d7
asrr #2,d7
suba n1,BASE_ROW
v(8)
v(7)
v(6)
v(5)
v(4)
v(3)
v(2)
v(1)
v 8 ( ) v 7 ( ) v 6 ( ) v 5 ( ) v 4 ( ) v 3 ( ) v 2 ( ) v 1 ( )
r0->BASE_ROW
Table 2. Read Out of Loop 2 Data
v(7)
v(6)
v(5)
v(4)
v(3)
v(2)
v(1)
v(6)
v(5)
v(4)
v(3)
v(2)
v(1)
; the same col.
; scale d6 and d7 by the devide
; routine scale factor
; scale the entry of L_matrix
; before saving to memory to
; prevent overflow
; write results to L_matrix
; end forloop L_matrix
; d8=d8+1, BASE_ROW=BASE_ROW-$34
; end forloop for moving pointer
; to previous col. in the cholesky
; matrix
v(5)
v(4)
v(3)
v(2)
v(1)
Implementation of the Algorithm
f
every iteration.
v(4)
v(3)
v(2)
v(1)
Equation 26
Equation 27
21