MGR10 A/B/C - Revision : I (for 7.0 software revision) 62
6.2.2.6 Device Dependent Messages (ATN False)
Data transferred on the DIO lines while the controller negates the ATN line (high) are Device
Dependent Messages. This is known as Data Mode. These messages are described fully in Section 4.
Serial Poll
A Serial Poll is a sequence which enables the controller to learn if a device or group of devices requires
service and/or determine multi bit status of devices on the interface.
Devices which can be Serial Polled will return a Status Byte (requires Talker subset) to the controller to
indicate their status under program control. The controller sequentially polls each individual device on
the interface (sends a SPE if IFC is false and sequentially addresses devices to talk) and evaluates each
status byte in turn. Therefore, this procedure can be lengthy in larger systems, but does provide the
nature of the request at the same time as the identity of the requestor.
It is advisable, though not mandatory, to poll every device to be sure to find every requestor and also to
send Serial Poll Disable (SPD) and Untalk (UNT) at the end of the procedure.
Parallel Poll
Parallel Poll is not implemented.
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