Alert Standard Format (ASF) Specification

Alert Standard Format (ASF) Specification v2.0 DMTF Document DSP0136
DSP0136 23 April 2003 Page 77 of 94
6 SMBus Device Characteristics
This section describes the behavior and requirements for SMBus devices that are defined by this
specification, ASF-sensor, legacy-sensor, and remote-control devices. The primary differences
between these device types are summarized below.
Legacy-sensor devices
• No well-defined or commonly accepted hardware interface for providing device information
(e.g. manufacturer, class, etc.)
• Primitive mechanisms for generating and clearing alert events
• No standard alert information associated with hardware events
• Only supports fixed slave addresses
ASF-sensor devices
• Well-defined hardware interface for providing device information
• A standard and consistent method for generating alert events regardless of sensor type
• A standard SMBus packet format for processing alert events
• Support for fixed address devices (i.e. system-resident) and dynamically addressed devices
(i.e. ARP-capable; PCI add-in card-resident)
Remote Control devices
• A defined SMBus transaction type (Byte Write).
• System defined values for various remote control actions.
6.1 Legacy Sensor Devices
If legacy sensor devices are included in an ASF managed client’s implementation, the client’s
firmware identifies the characteristics and access methods for the devices via the ASF_ALRT
ACPI data structure.
6.1.1 Sensor Requirements
To limit the scope of sensors supported by an alert-sending device, the following behavior must
be apply for a legacy-sensor device to be used in an ASF environment:
1. The alerts must be poll-able by doing an SMBus Byte Read message.
2. Individual status bits in the Byte Read’s Read Result value must identify the alerts.
3. The alert status bits must be either:
A. Level (always indicating the current status), or
B. Automatically cleared after the Byte Read is done, but set again before the next Byte
Read if the event is still active. The legacy-sensor device must clear the status within the
Minimum Legacy Sensor Poll Time specified by the managed client’s firmware, see
4.1.2.2 for more information.