Rainbow Electronics LM41 - Manual (Page 14)

1.0 Functional Description
(Continued)
All devices (master or slave) must monitor the bus for an
Attention Request signal. The following notes clarify the
intended system operation that uses the Attention Request
Indication.
• Masters are expected to use the attention request as a
trigger to read results from the LM41. This is done in a
sequence that covers all LM41s. This sequence is re-
ferred to as "master sensor read sequence".
• After an Attention Request is sent by an LM41 until after
the next read from the Device Status register the LM41
does not send Attention Requests for a function event
since it is guaranteed that the master will read the Status
register as part of the master sensor read sequence.
Note that the LM41 will send an attention for BER, re-
gardless of the Status register read, to help the master
with any error recovery operations and prevent dead-
locks.
• A master must record the Attention Request event. It
must then scan all slave devices in the system by reading
their Device Status register and must handle any pending
event in them before it may assume that there are no
more events to handle.
Note: there is no indication of which slave has sent the
request. The requirement that multiple requests are not sent
allows the master to know within one scan of register reads
that there are no more pending events.
1.3.6 Fixed Device Number Setting
The LM41 device number is defined by strapping of the ADD
pin. The LM41 will wake (after Device Reset) with the Device
Number field of the Device Number register set to the ad-
dress as designated in Section 2.3 "Device Number". It is the
responsibility of the system designer to avoid having two
devices with the same Device Number on the bus.
Devices should be detected by the master by a read opera-
tion of the Device Number register. The read returns "000" if
there is no device at that address on the bus (the EP bit must
be ignored).
LM41
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