Datasheet

LTC2977

2977fa

For more information www.linear.com/LTC2977

PMBus

COMMAND DESCRIPTION

MFR_COMMON

This command returns status information for the alert pin (ALERTB), share-clock pin (SHARE_CLK), write-protect pin

(WP), and device busy state.

This is the only command that may still be read when the device is busy processing an EEPROM or other command. It

may be polled by the host to determine when the device is available to process a PMBus command. A busy device will

always acknowledge its address but will NACK the command byte and set Status_byte_busy and Status_word_busy

when it receives a command that it cannot immediately process.

MFR_COMMON Data Contents

BIT(S) SYMBOL OPERATION

b[7] Mfr_common_alertb Returns alert status.

1: ALERTB is de-asserted high.

0: ALERTB is asserted low.

b[6] Mfr_common_busyb Returns device busy status.

1: The device is available to process PMBus commands.

0: The device is busy and will NACK PMBus commands.

b[5:2] Reserved Read only, always returns 1s

b[1] Mfr_common_share_clk Returns status of share-clock pin

1: Share-clock pin is being held low

0: Share-clock pin is active

b[0] Mfr_common_write_protect Returns status of write-protect pin

1: Write-protect pin is high

0: Write-protect pin is low

USER_DATA_00, USER_DATA_01, USER_DATA_02, USER_DATA_03, USER_DATA_04, MFR_LTC_RESERVED_1

and MFR_LTC_RESERVED_2

These registers are provided as user scratchpad and additional manufacturer reserved locations.

USER_DATA_00, USER_DATA_01, MFR_LTC_RESERVED_1 and MFR_LTC_RESERVED_2 are all reserved for

manufacturer use. Such uses include manufacturer traceability information and LTpowerPlay

features like the

CRC calculation and storage for user EEPROM configurations.

USER_DATA_02 is reserved for OEM use. These 2 bytes might be used for OEM traceability or revision information.

USER_DATA_03 and USER_DATA_04 are available for user scratchpad use. These 18 bytes (1 unpaged word plus

8 paged words)

might be used for traceability or revision information such as serial number, board model number,

assembly location, or assembly date.

All

user and OEM scratchpad registers may be stored and recalled from EEPROM using the STORE_USER_ALL and

RESTORE_USER_ALL commands.