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Document ID: PMC-2010146, Issue 4
98
PM2329 ClassiPI Network Classification Processor Datasheet
The logical E-Word Width is determined by scanning the D-Word Definition bits from DW6 down to
DW0, until it encounters the first D-Word field that is non-zero, i.e., D-Word that is not absent. The E-
Word width is C-Word plus the number of D-Words present.
E-RAM Width
Indicates the physical width of attached E-RAM. The PM2329 devices in cascade assume that the first
32 bits (i.e., C-Word) are connected to PM2329 #0, next 32 bits are also on CID #0, next 32 bits on CID
#1 and so on. This sequence must be maintained and gaps in the physical connection are not allowed.
The bits are written as follows:
001
32-bit
010
64-bit
011
96-bit
100
128-bit
101
160-bit
110
192-bit
111
224-bit
000
256-bit
Note that the PM2329 cascade allows a larger E-Word to reside in an E-RAM whose physical width is
smaller than the logical E-Word. This will happen whenever the D-Word Definition field indicates a
larger E-Word than what the E-RAM Width field specifies. Consequently, the number of locations
accessed to access the entire E-Word (E-Word Depth) varies. Given the E-Word width and E-RAM
width, the PM2329 automatically enforces a depth of 1, 2 or 4 as shown in the table below.
EMA[18:17] lines carry the ERAM depth field. For most efficient ERAM utilization, EMA[18] and
EMA[17] signals should be connected to the E-RAM devices depending on the depth of the E-Word as
shown in the table below.
Table 20
E-Word Depth Chart
E-Word Depth
for
E-Word Logical Width & E-RAM Physical Width Combinations
Physical
E-RAM
Width
(bits)
32
64
96
128
160
192
224
256
Logical E-Word Width (bits), C-Word plus D-Word
32
64
96
128
4
4
2
1
1
1
1
1
160
NA
4
2
2
1
1
1
1
192
NA
NA
4
2
2
1
1
1
224
NA
NA
4
2
2
2
1
1
256
NA
NA
4
4
2
2
2
1
Number
of
devices
required
1
1
2
3
4
5
6
7
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
4
2
1
1
1
1
1
1