ADLINK PCI-8258 - Manual (Page 208)

194 Motion Control Theory
EL signal is a hardware input signal including PEL and MEL. PEL
is the limit signal in positive direction and MEL the negative
direction one. An asserted EL signal causes the controller
responses with following actions:
1. If PEL signal is asserted for an axis in positive motion
status, the controller stops motion of the axis
immediately and error stop code of the axis is set to "4"
(STOP_PEL) and motion status of axis is set to
abnormal stop (ASTP = ON).
2. If MEL signal is asserted for an axis in negative motion
status, the controller stops motion of the axis
immediately and error stop code of the axis is set to "5"
(STOP_MEL) and motion status of axis is set to
abnormal stop (ASTP = ON).
3. If the axis is not in motion status and the PEL signal is
asserted then user's positive direction motion command
shall be ignored by the controller while error stop code of
the axis is set to "4" (STOP_PEL) and motion status of
axis is set to abnormal stop (ASTP = ON).
4. If the axis is not in motion status and the MEL signal is
asserted then user's negative direction motion command
shall be ignored by the controller while error stop code of
the axis is set to "5" (STOP_MEL) and motion status of
axis is set to abnormal stop (ASTP = ON).
5. There are two stop mode options available: decelerating
stop and immediate stop. The axis parameter code is
PRA_EL_MODE (0x02).