
Communication Layers' Attributes
Appendix D
D-12
The MAC (Media Access Control)–Layer attributes control the way in
which information is sent out onto the network. The OSI coprocessor’s
MAC–Layer attributes are listed in the following tables, along with a brief
description and the default settings for each.
ATTENTION: Your OSI coprocessor is shipped with its
MAC–Layer parameters pre–set to their Allen–Bradley default
values. Changing these values may cause severe
communication problems. Refer to the Allen–Bradley MAP
Station Manager User’s Manual (publication 6630–6.5.2) for
details on changing them.
ATTENTION: Each device on your MAP 802.4 token–passing
network must have the same slot time. Failure to set the slot
time correctly may severely affect the operation of the network.
MAC Layer
Parameter:
Description:
Default Value:
MAC address
The IEEE 802.4 address of this node
802.4 default values are created
to be globally unique. This value
is defined in PROM.
Group Address 1
through 8
A logical OR is performed on these group
addresses to obtain the group address mask.
This mask is used to determine if a frame
specifying a group address should be accepted
by this node.
(1) 09 00 2B 00 00 04
(2) 41 5F 42 49 50 4C
(3) 01 00 00 00 00 00
(4) 01 00 00 00 00 00
(5) 01 00 00 00 00 00
(6) 01 00 00 00 00 00
(7) 01 00 00 00 00 00
(8) 01 00 00 00 00 00
High priority token hold
time
Specifies the maximum amount of time (in
octets) the node can transmit data before
passing the token.
FFFF (Hex) 65535 (Decimal)
Priority 0 token hold
time
Maximum amount of time (in octets) this station
can transmit from this queue.
FFFF (Hex) 65535 (Decimal)
Priority 2 token hold
time
Maximum amount of time (in octets) this station
can transmit from this queue.
FFFF (Hex) 65535 (Decimal)
Priority 4 token hold
time
Maximum amount of time (in octets) this station
can transmit from this queue.
FFFF (Hex) 65535 (Decimal)
Target rotation time for
ring maintenance
In conjunction with maximum inter solicit count
and ring maintenance timer initial value, this
parameter controls the frequency at which a
node solicits successors.
1FFFFF (Hex) 2097151
(Decimal)
Ring maintenance
initial value
Used in determining when a station solicits.
1FFFFF (Hex) 2097151
(Decimal)
MAC Layer Attributes
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