ISL5216_05 Datasheet, PDF (21/65 Pages) Intersil Corporation – Four-Channel Programmable Digital DownConverter

ISL5216
BIT
POSITIONS
63
66:64
75:67
84:76
93:85
95:94
104:96
106:105
115:107
117:116
119:118
122:120
INSTRUCTION BIT FIELDS (Continued)
FUNCTION
DESCRIPTION
Reserved
Set to 0.
Coefficient Memory 66:64
Block Size
0
Memory Block Size
8
1
16
2
32
3
64
4
128
5
256
6
512
7
1024
(Modulo addressing can be used, but is usually not needed. If not needed this bit field can always be
set to 7).
Number of FIR
Outputs
Number of FIR outputs (range is 1 to 512, load w/ desired value minus 1).
This is usually equal to the total decimation that follows the filter.
Read Address
Pointer Step
Read address pointer step (for next run). This is usually equal to the filter decimation times the number
of outputs from the instruction.
Initial Address Offset Initial address offset (to ADDRB). This is the offset from the start address to other end of filter.
For symmetric filters, usually equal to -1 x (number of taps -1).
Reserved
Set to 0
Memory Reads Per
FIR Output
This is based on the number of taps (load with value below minus 1).
Type
Value
Symmetric, even number of taps (taps/2) or floor((taps+1)/2).
Symmetric, odd number of taps
Decimating HBF
(taps+1)/2 or floor((taps+1)/2).
(taps+5)/4.
Asymmetric
taps.
Complex
Resampling
taps .
taps/phase (six taps per phase for the ROM’d coefficients provided).
Interpolating HBF
(taps+5)/4-1 .
Clocks Per
Memory Read
Set to 0 for all but complex FIR, which is set to 1.
Data Memory
Step Size 1
(ADDRA) Step size for all but the last tap computation of the FIR.
Set to -2 for HBF, -1 otherwise.
Data Memory
Step Size 2
(ADDRA) Step size for last tap computation. Set to -1.
117:116 Step size
0
0
1
-1
2
-2
3
step size value.
Data Memory
(ADDRB) Step size for opposite end of symmetric filter. Set to +2 for Decimating HBF, to +1 for others
Address Offset Step (the B data is not used for asymmetric, resampling, and complex filters).
Coefficient Memory
Step Size
(ADDRC) Usually set to 1.
122:120 Step size
0
0
1
1
2
2
3
4
4
8
5
16
6
32
7
64
21
July 8, 2005