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
to Transmit to
this ID?
N
N
TA?
Y
Y
Y
N
Free Buffer
Enquiry to
this ID?
N
Y
Y
RI?
N
Write SID
to Buffer
No Activity
for 82
uS?
Y
Broadcast
Enabled?
Y
N
Set NID=ID
Start Timer:
T=(255-ID)
x 146 us
Activity
On Line?
N
CRC
OK?
Y
OK?
N
N
T=0?
Y
Y
N
SOH?
N
Transmit
NAK
Transmit
ACK
N
RI?
Broadcast?
Y
Send
Packet
Transmit
Free Buffer
Enquiry
N
ACK?
Y
No
Activity
for 74.7
us?
N
1
Y
DID
=0?
N
DID
=ID?
N
Y
Y
Was Packet
Broadcast?
N
No
Activity Y
for 74.7
us?
N
N
ACK?
Y
Y
NAK?
Set TA
Write Buffer
with Packet
Pass the
Token
Set TA
Increment
NID
Set TMA
Y
No
Activity
for 74.7
us?
N
LENGTH
N
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
=0?
Y
Set RI
N
DID
=ID?
N
Y
SEND ACK
FIGURE 1 - COM90C66 OPERATION
8
SMSC [ SMSC CORPORATION ]
