Allen-Bradley 1784-KTX Reference Manual page 64

Chapter 6
Reporting KTx Scanner Status
6-4
Adapter Fault Byte
The host uses the adapter fault byte to determine the current state of an
adapter and its relationship to a fault dependent group. This table defines
the bits of the adapter fault byte.
Bit # Mnemonic
0-3 fault_group_number
4 in_fault_group
5 adapter_online
6 adapter_group_faulted
7 undefined
Adapter Retry Count Byte
When an adapter fails to reply to a scanner command or when a
communication error is detected in the adapter's reply, the scanner will
retransmit or 'retry' the command to the adapter. The scanner records the
number of retries for each adapter in the scan list by incrementing the
adapter's retry count byte. A large count in this byte indicates the adapter
is not communicating reliably with the scanner.
The scanner will retry a discrete I/O command to an adapter two times. If
the adapter fails to respond with a valid reply to the final retry, the scanner
considers the adapter to be faulted and clears the
adapter's
adapter_fault_byte
command to an adapter. If the adapter fails to respond with a valid BT
reply to the retry, the scanner notifies the host via a confirmation that the
BT failed. In the case of a failed BT, however, the scanner does not
consider the adapter to be faulted and does not change the
Indexing into the Adapter Status Table
In Example 6.A (extracted from the example header file ktx_dp.h), the
adapter status table is declared as an array with 128 members. Each
member consists of an adapter configuration byte, an adapter fault byte,
and an adapter retry count byte. Simply use the adapter address to index
into the array. The code fragment shows how to read the size of the
adapter from the adapter status table when the adapter's address is 12.
size = dp–>adapter_status_table[12].adapter_config_info.size;
Description
Fault group is identified by a number, 0-15.
When set, this adapter is in the fault group.
When set, this adapter is on line, i.e., it is active on
the link.
When clear, this adapter is not responding to
scanner commands.
When set, at least one adapter in the fault group
is faulted.
Reserved for future use.
adapter_online
. The scanner allows one retry for a BT
bit in the
bit.
adapter_online