1. SCD: TCAM Library Fred Kuhns Applied Research Laboratory
Applied Research Laboratory
Washington University in St. Louis

2. Assumptions, Constants
TCAM located on SRAM0 (SRAM, channel ID 0)
Base address 0x ; Select 0 and burst size 1.
Each NPU (A/B) has own LA-1 interface
SPP version 1 and 2 do not use the second LA-1 interface
set IsPort1Used to 0 (i.e. false)
NPUA must perform initial configuration
Both NPUA/B can use LA-1 interface for lookups
All TCAM control implemented on XScale A
its not clear that we can use the IDT libraries to control from both NPUA and NPUB.
All databases are IDT type exact match.
Maximum of 16 databases;
Must start on segment boundary
User specified DB entry widths:
Max: 576-bits; Min: 32-bits; Allowed sizes: n*32, n in (1, 18); 36; 74 and 144.
Actual Core sizes: 36, 72, 144, 288 and 576 bits
Segment size: 8K x 72-bit
256K x 72-bit core entries
Database must start on a segment boundary.
Max segments: 32
ZBT Associated SRAM
512K x 36 bit ZBT SRAM (18Mb)
Allocated as 0, 32, 64 or 128-bit result data
Index and size are number of 32-bit words
Command context
Available: 128 (0,...,127)
Control uses context 120 through 127

3. Search Machine Class Class SearchMachine {...}
May use callbacks with interrupt handlers for ARP aging.
Constructor accepts a set of key value pairs specify the configurable parameters.
typedef multimap<string, valTable> confTable;
Internal state:
next database id, starts at 0.
segment allocation state (for the 32 available segments): Just need current address of available block.
associated memory allocation state: Just need current address of available block.
current set of database objects (stl set object).
Operations: The Database object is of type Handle<T,P> with the RefCntPolicy (reference counted smart pointer). Or can use pointers by then the SearchMachine class “owns” the DB object and is the only one allowed to destroy it.
typedef handle<Database,RefCntPolicy> DB;
DB create_database(key_bits, res_bits, max_cnt);
void destroy_database(DB);
get_dbs() // returns an iterable object, say an stl set.

4. Configuring a DataBase
class DataBase {...}
The user is expected to keep track of entry indices.
State:
id_; // returns ID assigned by SearchMachine class
handle_; // assigned by IDT software when DB is created
key_width(); // in bits
core_width(); // in bits
result_width(); // in bits
entry_count(); // max number of entries
core_start_addr_;
assoc_data_addr_;
Operations:
fltr {key[N]; mask[N]; result[M]}
write_fltr(index, fltr);
update_result(index,result);
fltr get_fltr(key); fltr get_fltr(index)
result lookup_fltr(key)
rem_fltr(fid); rem_fltr(key)

5. Configuration File [SearchMachine] useLAPort1 = 0 [database]
name = name_db1
id = num_db1
numEntries = X
keyWidth = W # bits
resultWidth = Y # bits
...

6. Substrate Configuration tables on NPE
Search machine
TCAM
NPUA
NPUB
Entries
masks
keys
results
... 1 2
NA-1 NA
NA+1
N-1
NA+2