HIPPI
S2020/S2021 SOURCE DEVICE STATE MACHINES
REQ REQuest signal from the HIPPI channel. The
functions of this signal are defined in the HIPPI-PH
spec. When debounced and synchronized as
<SYNCREQ> this signal is used in the input ‘alpha-
bet’ decoder for the Connect Control SM.
{IDLDSAB} THE IDLe DiSABled state is entered from
the {DISABLED} state, the {IDLENAB} state, and
from the {REJCOMPL} state when the “IDSB” de-
code is true. This state will persist until the “IDSB”
decode is false. The normal exit from this state is to
the {IDLENAB} state if the “IENB” decode is true.
The “DSBL” decode will force exit to the {DIS-
ABLED} state. Any other decode forces the
{HANGERR} state.
CONIN CONnect IN signal from the Destination Host
system. This signal when asserted during a Connec-
tion Request cycle, indicates an active response to
the Request by the Destination Host system.
{IDLENAB} The IDLe ENABled state is entered from
the {DISABLED} state, the {IDLENAB} state, and
from the {REJCOMPL} state when the “IENB” de-
code is true. This state will persist until the “IENB”
decode is false. This state is exited to the
{REQCON} state if the “RQCN” decode is true, the
{ACC0} state if the “CNAC” decode is true, the
{REJ0} state if the “CNRJ” decode is true, and the
{IDLDSAB} state if the “IDSB” decode is true.
If this signal is asserted prior to the detection of a
Connection Request cycle, the “IDSB” decode inhibits
response to Requests from the HIPPI channel.
If this signal remains low after an asserted REQ
from the HIPPI channel, the channel remains ‘hung’
in the Connection Request state until the Remote
Source exercises a time-out of the unanswered re-
quest. The CONIN signal may be tied directly to the
CONRQ output, and the ACCRJ used as the active
Connection control by the Destination Host system.
{REQCON} The REQuest CONnection state is entered
from the {IDLENAB} state at the detection of an
asserted REQ from the HIPPI channel while
CONIN is deasserted (“RQCN” decode is true).
This state will persist while “RQCN” remains true. If
the REQ is deasserted, this state is exited to the
{IDLENAB} state. This state is exited to the {ACC0}
state if the “CNAC” decode is true, the {REJ0} state
if the “CNRJ” decode is true, the {IDLENAB} state if
the “IENB” decode is true and the {IDLDSAB} state
if the “IDSB” decode is true.
ACCRJ ACCept/not ReJect signal from the Destination
Host system. This signal together with the CONIN
signal described above, control the Destination
device’s response to a Connection Request (as-
serted REQ) from the HIPPI channel remote
Source. If a ‘1’ is placed on this input, the accompa-
nying active CONIN is considered as an accep-
tance response to the Connection Request. If a ‘0’
is placed on this input, the asserted CONIN will
result in an active Rejection of the Connection Re-
quest (the CON signal to the HIPPI channel will be
asserted for four clock cycles only, then
deasserted). The active Rejection avoids possible
‘hung’ conditions on the HIPPI channel.
{ACC0-3} The ACCept 0 through ACCept 3 states are
entered at {ACC0} from either {IDLENAB} or
{REQCON} when the “CNAC” decode is true.
These states are then sequenced in order unless
overridden by a “DSBL” decode. The CON signal is
asserted on the HIPPI channel for these states.
This sequence is exited to the {CONNECTED}
state if the “DSBL” decode remains false.
CONNECT STATE MACHINE INTERNAL
INPUTS
{CONNECTED} The CONNECTED state is entered
when a valid Connection is established across the
HIPPI channel between the Destination and the
Source. This state enables the output of the RDY
signals on the HIPPI channel to initiate the transfer
of Burst data from the remote Source. This state
will persist while either the “CNAC” or the “CNRJ”
decodes are true and the “DSBL” decode remains
false. The CON signal on the HIPPI channel re-
mains asserted while in this state. This state is ex-
ited to the {REJCOMPL} state if the “RQCN”
decode is true, the {DISCON0} state if the “IENB”
decode is true, and the {INCOMPDCON} state if
the “IDSB” decode is true.
<RSTCON> ReSeT CONnection signal from the internal
Data/FIFO Control SM. This signal is asserted dur-
ing error states of the DATA/FIFO SM. When as-
serted, this signal is sufficient to force the internal
“DSBL” decode independent of other inputs.
CONNECT SM INTERNAL STATES
{DISABLED} The DISABLED state of the Connect SM
is forced by the decode of “DSBL” from the input
‘alphabet’. “DSBL” will force this state from all other
states of the Connect SM. While in this state the
SRCAV output is held to ‘0’. This state is exited to
the {IDLDSAB} state if the “IDSB” decode is true
(CONIN asserted with no REQ active). The
{IDLENAB} state will be entered if the “IENB” de-
code is true.
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