COM90C66 Datasheet, PDF (8/76 Pages) SMSC Corporation – ARCNET Controller/Transceiver with AT Interface and On-Chip RAM

Power On
Reconfigure
Timer has
Timed Out
Send
Reconfigure
Burst
Read ID* From
Switches
Write ID to
RAM Buffer
1
Set NID=ID
Start
Reconfiguration
Timer (840 mS)
Y
Invitation
N
to Transmit to
this ID?
N
Y
TA?
Transmit
NAK
Y
Free Buffer
Enquiry to
this ID?
Y _RI? N
N
Y _SOH? N
Y
N
RI?
Broadcast?
N
Y
Send
Packet
Transmit
ACK
Was Packet ^Y
Broadcast?
Transmit
Free Buffer
Enquiry
N
ACK?
No
Activity
for 74.7
us?
Y
N
NAK?
Write SID
to Buffer
Y
Set TA
DID ^Y
=0?
N
DID
=ID?
YN
Broadcast
Enabled?
Y
1
Write Buffer
N
with Packet
No
Activity
Y
for 74.7
us?
N
Set TA
N _ACK? Y
Set TMA
Increment
NID
Y
No
Activity
for 74.7
us?
Pass the
Token
CRC ^N
N
OK?
Y
LENGTH ^N
OK?
Y
*The ID set by the external switches is continually sampled during COM90C66
operation.
- ID refers to the identification number of the ID assigned to this node.
- NID refers to the next identification number that receives the token after
this ID passes it.
- SID refers to the source identification.
- DID refers to the destination identification
- SOH refers to the start of header charcter; preceeds all data packets.
DID ^Y
=0?
N
DID ^N
=ID?
Y
SEND ACK
N
Set RI
No Activity N
for 82
uS?
Y
Set NID=ID
Start Timer:
T=(255-ID)
x 146 us
Activity ^Y
On Line?
N
N
T=0?
Y
FIGURE 1 - COM90C66 OPERATION
8