2.1
Block Diagram
2.2
Redundant MMC Flash & FWUM
The MMC microcontroller runs a firmware from its internal 256KB flash. It is programmed by an
other microcontroller named FWUM (FirmWare Update Manager). The FWUM keeps the last two
copies of the MMC firmware in dedicated flash memories. The FWUM act as a watchdog to the MMC
and can rollback a firmware update in the MMC in case of problems.
The FWUM itself is a microcontroller with internal flash to store MMC firmware image. This
microcontroller is also an external watchdog for the MMC. Functions of this microntroller is kept to
a minimum. The FWUM firmware is field updatable.
Note:
The MMC and the FWUM have an internal hardware watchdog.
2.3
Hardware Management Overview
The AMC Carrier communicates with the Module Management Controller (MMC) using the IPMB_L
channel.
The memory subsystem of the MMC consists of an integrated flash memory to hold the MMC
operation code and integrated RAM for data. The field replacement unit (FRU) inventory
information is stored in the nonvolatile memory on an EEPROM connected via a local I2C interface
to the MMC microcontroller. It is possible to store up to 4 KBytes within the FRU inventory
2-5
AM4520 User’s Guide
