Addressing And Communications; Device Addressing; Communication Recommendations - Analog Devices LT7170 Reference Manual

Reference Manual LT7170/LT7170-1

ADDRESSING AND COMMUNICATIONS

DEVICE ADDRESSING

The LT7170/LT7170-1 offer addressing modes that provide flexible ways to control multiple channels at once or individually.
Device addressing is the standard way to communicate with a single instance of the LT7170/LT7170-1. The value of the device address is
set by the MFR_ADDRESS command. Device addressing can be disabled by writing a value of 0x80 to the MFR_ADDRESS command. If
MFR_ADDRESS cannot be read from NVM due to an NVM fault, the device address is set to 0x7C.
Global addressing provides a means to address all LT7170/LT7170-1 devices on the bus. The LT7170/LT7170-1 global addresses are fixed
at 0x5A (7-bit notation) and 0x5B. They cannot be disabled. Do not read from global addresses because multiple devices may respond
simultaneously. Other Analog Devices, Inc., device types may respond at one or both of these global addresses.
Rail addressing provides a means to control multiple channels simultaneously. While similar to global addressing, the rail address can be
dynamically assigned with the MFR_RAIL_ADDRESS command, allowing any logical grouping of channels that may be required for reliable
system control. Do not read from rail addresses because multiple devices may respond.
Zone write addressing provides a means to write to a set of channels. The set of channels can be distributed across multiple devices. Each
channel is programmed to be part of a zone by programming the selected zone number to the ZONE_CONFIG command. This configuration
only needs to be performed once. After zone configuration, the bus controller uses the ZONE_ACTIVE command to select the active zone.
If the configured zone of a channel matches the active zone, or the active zone is set to all zone, the channel responds to subsequent
ZONE_WRITE operations. A ZONE_WRITE operation is started when the bus controller uses the ZONE_WRITE address (0x37, 7-bit notation)
as the device address in an SMBus write command.
All means of PMBus addressing require the user to employ disciplined planning to avoid addressing conflicts. Communication to LT7170/
LT7170-1 devices at global and rail addresses are limited to command write operations.

COMMUNICATION RECOMMENDATIONS

If PMBus commands are received faster than they are being processed, the LT7170/LT7170-1 may become too busy to handle new
commands. If a command is written when the LT7170/LT7170-1 are busy processing a command, the devices ignore that command, set Bit 7 of
STATUS_BYTE, and pull the ALERT pin low. Bit 6 of MFR_COMMON sets to a 1 when the LT7170/LT7170-1 are ready to accept commands.
This bit can be polled before writing commands. Alternatively, clock stretching can be enabled. Clock stretching is enabled by setting Bit 1 of
MFR_CONFIG_ALL_LT7170.
NVM commands may take longer to process, including STORE_USER_ALL and MFR_COMPARE_USER_ALL. In these cases, either poll Bit 6
of MFR_COMMON or enable clock stretching to avoid a busy condition.
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