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On-board RAM can be used to store NTDS input, output, EF and EI buffers. It is also possible to download user programs to on-board RAM at the beginning of runtime and thereby limit VMEbus usage during real-time operations to only those required for the transmission of NTDS buffer data. The Dual E board also provides a user program trace feature. When invoked, a program trace file is generated which contains a sequential list of user instructions as executed by the board. This file can be stored in a circular queue located in on-board RAM. The user can retrieve this trace file to recover detailed information regarding the sequence of instruction execution. This feature can prove especially useful when the user's program and associated variables have been stored in on-board RAM and their execution is not visible on the VMEbus. All remaining RAM can be configured as global VME memory as required by other resources in the VME system. The Dual E board also contains 2 Mbytes of FLASH memory which is used to archive firmware for all programmable components. FLASH memory also contains the lookup table used to correlate each user’s specific instruction set with a generalized set of ‘C’ subroutines which perform NTDS I/O. See the section "Flexible Instruction Set" for more information about the lookup table. FLASH memory is also capable of storing a sequence of user programmed instructions to be performed at any point during operation including start up. This would, for example, allow users to store chains in non volatile FLASH memory to be loaded automatically into RAM upon power-up for execution without using the VMEbus. |
