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Cam Interface - Motorola MC68838 User Manual

Media access controller
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Transmit Parity (TPRITY)
This TTL-level input signal indicates the parity of the TPATHx bus; the TXCTLx lines are
not affected. The MAC expects either odd parity or no parity according to the
TX_PARITY_ON bit value in control register B. TPRITY is checked on every cycle,
including FILLER. This signal must be synchronous to BYTCLK.
Transmit Ready (TXRDY)
This output signal indicates to the FSI that the MAC is ready to accept additional
TXDATx transfers.
Abort Transmission (TABORT)
This output signal indicates to the FSI that it should abort this transmission. This signal
is asserted while the transmitter is turned off (i.e., MAC_ON = 0).

4.6 CAM INTERFACE

The CAM interface is a BYTCLK-synchronous interface used to connect the MAC to
external address or frame routing control recognition logic such as CAM chips, FSI internal
CAM, or source routing control logic.
Load Address/Transparent Bridge Forward (LDADDR/ TR_BR_FWD )
This bidirectional control signal is used for CAM interface. As a CMOS-level output,
LDADDR is pulsed high for one BYTCLK cycle just before the first byte of the DA or SA
field is presented on the RCDATx bus. As a TTL-level input, TR_BR_FWD is used as a
match signal in the extended match timing mode as defined and controlled by the
EXT_DA_MATCH bit in control register B. TR_BR_FWD is asserted low.
Address 16/Receive Abort 2 ( ADDR16 /RABORT2)
This bidirectional control signal is used for CAM interface. As a CMOS-level output,
ADDR16 represents the last L-bit received. The L-bit is a bit in the FC field of all frames
and tokens. It is high when a frame with a 48-bit address field is received and low when
a frame with a 16-bit address field is received. It is high for restricted tokens and low for
unrestricted tokens. This line is synchronous with BYTCLK. As a TTL-level input,
RABORT2 provides a second abort signal to indicate that the MAC should abort the
incoming frame. The MAC will signal end of data to the FSI. The functionality of this
input is the same as the current RABORT input. This signal line is controlled by the
RABORT2 bit in control register B.
Destination Address (DA)
This CMOS-level output signal is used to indicate whether the address being presented
to the CAM is the DA or SA field of the received packet. This signal is low when the
MAC is receiving fields other than address fields.
MOTOROLA
MC68838 USER'S MANUAL
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