PPMAC - Invalid lookahead definition when switching CS Groups

[LeandroMartinsdS]

The redefineLookaheads method currently uses commands that are exclusive to TurboPMAC, making it ineffective for PowerPMAC. This difference can lead to incorrect or non-existent allocation for coordinate systems when switching between defined CsGroups.

Key differences between TurboPMAC and PowerPMAC that are relevant to this issue include:

• PowerPMAC does not require a specific order to define lookahead buffers for each coordinate system, unlike TurboPMAC which requires definition from high-numbered to low-numbered coordinate systems.

• PowerPMAC has a minimum lookahead buffer size of 1024.

• PowerPMAC only accepts the define lookahead command for coordinate systems that have a number of assigned motors greater than zero. Although it is possible to directly set Coord[x].LHSize (which reflects the buffer size defined by the define lookahead command) without any restriction on the number of motors assigned, it is unclear if the allocation occurs correctly. As per the Power PMAC Software Reference Manual (May 19, 2023, p.853), it is stated that “it is not possible to write to it directly in the Script environment.”

This issue is to keep track of the changes necessary to ensure compatibility of the redefineLookaheads method with both TurboPMAC and PowerPMAC, and to guarantee correct lookahead definition when switching between CS Groups, regardless of the PPMAC type in use.