WidePort LANCAM® Family
PIN DESCRIPTIONS
All signals are implemented in CMOS technology with TTL levels. Signal names that start with a slash (“/”) are active LOW. Inputs
should never be left floating. The CAM architecture draws large currents during compare operations, mandating the use of good layout
and bypassing techniques. Refer to the Electrical Characteristics section for more information.
of the device (/MF=/MI). /MF is HIGH if there is no match
or when the daisy chain is disabled (/E goes HIGH when
/EC was HIGH on the previous falling edge of /E). The
System Match flag is the /MF pin of the last device in
the daisy chain. /MF will be reset when the active
configuration register set is changed.
/E (Chip Enable, Input, TTL)
The /E input enables the device while LOW. The falling
edge registers the control signals /W, /CM, /EC. The rising
edge locks the daisy chain, turns off the DQ pins, and clocks
the Destination and Source Segment counters. The four
cycle types enabled by /E are shown in Table 2.
/MI (Match Input, Input, TTL)
/W (Write Enable, Input, TTL)
The /MI input prioritizes devices in vertically cascaded
systems. It is connected to the /MF output of the previous
device in the daisy chain. The /MI pin on the first device in
the chain must be tied HIGH.
The /W input selects the direction of data flow during a
device cycle. /W LOW selects a Write cycle and /W HIGH
selects a Read cycle.
/CM (Data/Command Select, Input, TTL)
The /CM input selects whether the input signals on
DQ31–0 are data or commands. /CM LOW selects Command
cycles and /CM HIGH selects Data cycles.
/MA (Device Match Flag, Output, TTL)
The /MA output is LOW when one or more valid matches
occur during the current or the last previous compare
cycle. The /MA output is not qualified by /EC or /MI,
and reflects the match flag from that specific device’s
Status register. /MA will be reset when the active register
set is changed.
/EC (Enable Daisy Chain, Input, TTL)
The /EC signal performs two functions. The /EC input
enables the /MF output to show the results of a comparison,
as shown in Figure 6. If /EC is LOW at the falling edge of /E
in a given cycle, the /MF output is enabled. Otherwise, the
/MF output is held HIGH. The /EC signal also enables the
/MF–/MI daisy chain, which serves to select the device
with the highest-priority match in a string of LANCAMs.
Tables 6a and 6b explain the effect of the /EC signal on a
device with or without a match in both Standard and
Enhanced modes. /EC must be HIGH during initialization.
/MM (Device Multiple Match Flag, Output, TTL)
The /MM output is LOW when more than one valid
match occurs during the current or the last previous
compare cycle. The /MM output is not qualified by /EC
or /MI, and reflects the multiple match flag from that
specific device’s Status register. /MM will be reset when
the active register set is changed.
/FF (Full Flag, Output, TTL)
DQ31–0 (Data Bus, Three-state I/O, TTL)
The DQ31–0 lines convey data, commands, and status to
and from the WidePort LANCAM, as shown in Table 3. /W
and /CM control the direction and nature of the information
that flows to or from the device. When /E is HIGH, DQ31–0 go
to HIGH-Z.
If enabled in the Control register, the /FF output goes LOW
when no empty memory locations exist within the device
(and in the daisy chain above the device as indicated by
the /FI pin). The System Full flag is the /FF pin of the last
device in the daisy chain, and the Next Free address resides
in the device with /FI LOW and /FF HIGH. If disabled in the
Control register, the /FF output only depends on the /FI
input (/FF = /FI).
/MF (Match Flag, Output, TTL)
The /MF output goes LOW when one or more valid
matches occur during a compare cycle. /MF becomes
valid after /E goes HIGH on the cycle that enables the
daisy chain (on the first cycle that /EC is registered LOW
by the previous falling edge of /E; see Figure 6). In a
daisy chain, valid match(es) in higher priority devices
are passed from the /MI input to /MF. If the daisy chain
is enabled but the match flag is disabled in the Control
register, the /MF output only depends on the /MI input
/FI (Full Input, Input, TTL)
The /FI input generates a CAM-Memory-System-Full
indication in vertically cascaded systems. It is connected
to the /FF output of the previous device in the daisy chain.
The /FI pin on the first device in a chain must be tied LOW.
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