com90c66 Standard Microsystems Corp., com90c66 Datasheet - Page 8

• Manufacturer Part Number: com90c66
• Description: Arcnet Controller/transceiver With At Interface And On-chip Ram Corporation
• Manufacturer: Standard Microsystems Corp.

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