Download Print this page

Motorola MC68838 User Manual page 39

Media access controller
Hide thumbs

Advertisement

RING_OP_CHNG—RING_OPERATIONAL Flag Changed
This bit is set when RING_OPERATIONAL changes from zero to one or vice versa.
BAD_T_OPR—T_OPR < Target Request Time Register when Ring Is Operational
This bit is set when the transmitter FSM takes the Recovery_Required transition
because RING_OPERATIONAL and T_Opr < target request time register is true. This
can only happen when A MAC_RESET of this station, causing TRT time remaining
register to equal T_Max and RING_OPERATIONAL to be cleared, is followed by the
receipt of a token (Pass_Actions performed), which causes RING_OPERATIONAL to be
set and T_Opr to now equal T_Max (since TRT time remaining register still equals
T_Max), before my claim or a higher claim is received (since that recomputes the TRT
time remaining register). If LOSE_CLAIM is true, this bit is not set since the MAC
ignores the RING_OPERATIONAL AND T_Opr < T_Req condition (i.e., no transition is
taken in this case).
TVX_EXPIR—TVX Timer Expiration
This bit is set when the TVX timer expires and causes a Recovery_Required transition in
the transmitter FSM. This bit is not set when the TVX expires if LOSE_CLAIM is true or
the transmitter FSM is in the Tx_Claim or Tx_Beacon state, since the timer expiration in
this case causes no state transition.
LATE_TKN—TRT TIMER Expiration when LATE_CT > 0
This bit is set when the TRT timer expires and causes a Recovery_Required transition in
the transmitter FSM. This bit is not set when the TRT expires if LOSE_CLAIM is true or
the transmitter FSM is in the Tx_Claim or Tx_Beacon state, since the timer expiration in
this case causes no state transition.
RCVRY_FAIL—Recovery Failure
This bit is set when the TRT timer expires while the transmitter FSM is in the Tx_Claim
or Tx_Beacon state (unless there is some overriding transition caused by, for example,
a MAC_RESET or a claim/beacon received). It is possible for this bit to be set even if
LOSE_CLAIM is true.
DUPL_TKN—Duplicate Token Detected
This bit is set when the transmitter believes that it is holding the token (i.e., when the
transmitter FSM is in the Tx_Data, Tx_Token, Tx_Void, or FDX states) and a token is
received.
DUPL_ADDR—Duplicate Address Detected
This bit is set when a frame is received with a matching individual DA and the received
A indicator is an S-symbol (meaning that another station also matched this individual
address). Specifically, this bit is set when A_FLAG = true and E_FLAG = false, and the
I/G bit of the DA = 0, and Ar = S-Symbol.
The A_FLAG is only set upon matching the broadcast address (subject to
DISBLE_BRDCST being applicable since no group addresses are considered) or
MOTOROLA
MC68838 USER'S MANUAL
3- 19

Advertisement

loading

  Related Manuals for Motorola MC68838