Set and Reset Wait Bits Command

Character: none
Decimal: 23
Hexadecimal: 0x17
Command Value: Bits to Reset : Bits to Set

Note: This command is supported in RMC100 CPU firmware dated 20060216 or newer.

The RMC100 has 8 internal bits that can be used as semaphores. These bits can be set and reset using the Set and Reset Wait Bits command. These same internal bits can be tested with the Check Wait Bits link type. This allows an axis' task to signal other tasks or allows a task to wait until some event has happened.

The 16-bit Command Value is split into two bytes. The upper 8 bits specify which bits are to be cleared. For example, setting bits 8 and 10 of the Command Value would clear wait bits 0 and 2. Likewise the lower 8 bits specify the bits to be set. It is possible to set and clear multiple bits with just one command.

Example:

Axis 4 may need to know when axes 0 to 3 have cleared a position. The step sequence running on Axis 4 would set wait bits 0 to 3 and then wait for axis 0 to 3 to clear their bit. When all four bits are cleared then axis 4 would know it is safe to proceed. Axis 4 would use the check wait bits link type to insure that wait bits 0 to 3 are cleared before proceeding. It is much easier for axis 4 to do just one check for the 4 wait bits to be cleared than doing four individual enhanced links that check axis 0 to 3's position one by one.

Note: Wait bit 7 is used by the Profibus DP communications so the user can tell when spline downloads are finished. The Profibus DP spline processing routine sets wait bit 7 when a download to the spline area is detected. The bit is cleared when the download is done. The user can then use the step table and the Check Wait Bits link to be sure the spline is ready before executing the spline.