WIENER, Plein & Baus GmbH
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www.wiener-d.com
7 PROTECTED OPERATIONS
There are four kinds of operations that can be performed only after a special “unlock”
sequence is issued. These are:
(i)
Erase SPI memory
(ii)
Program SPI memory
(iii)
Reboot
(iv)
Exit from passive mode.
For the first three of the above operations, the requirement for an “unlock” serves the purpose
of avoiding inadvertent corruption of the configuration SPI memory or inadvertent rebooting
of VM-DBA.
As far as the exit from the passive mode is concerned, unlocking is necessitated by the fact
that while in passive mode, VM-DBA is not responsive to regular commands but still checks
for the receipt of the “unlock” sequence. Then, upon detecting “unlock” it responds to the
subsequent “exit from passive” command and only to that one.
7.1
The Unlock Sequence
The
unlock sequence
consists of two consecutive A24/D32 “write” commands to the address
offset of 0x55554 of data words, first 0x55555555 and then, 0xAAAAAAAA. It is valid
only for the operation that directly follows the sequence.
8 SPI MEMORY OPERATIONS
There are two SPI memories on-board to store two FPGA configuration files. The FPGA first
boots from the memory selected by a respective jumper. Upon a successful boot, VM-DBA
allows the following operations involving the SPI memory:
(i)
Selecting a particular target SPI memory, regardless of the default-boot jumper
setting.
(ii)
Write enabling a particular SPI memory.
(iii)
Erasing the selected memory (a protected operation requiring prior unlocking).
(iv)
Checking the status of the erase operation.
(v)
Programming the selected memory – memory must be erased prior to
programming (both operations require prior unlocking)
(vi)
Checking the status of programming.
(vii)
Rebooting from the selected SPI memory (a protected operation requiring prior
unlocking).
