LM628, LM629

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SNVS781C – JUNE 1999 – REVISED MARCH 2013

Table 3. Mask and Reset Bit Allocations for Interrupts

Bit Position

Function

Bits 15 thru 7

Not Used

Bit 6

Breakpoint Interrupt

Bit 5

Position-Error Interrupt

Bit 4

Wrap-Around Interrupt

Bit 3

Index-Pulse Interrupt

Bit 2

Trajectory-Complete Interrupt

Bit 1

Command-Error Interrupt

Bit 0

Not Used

RSTI COMMAND: RESET INTERRUPTS

Command Code: 1D Hex

Data Bytes: Two

Data Range: See Text

Executable During Motion: Yes

When one of the potential interrupt conditions of Table 3 occurs, command RSTI is used to reset the

corresponding interrupt flag bit in the status byte. The host may reset one or all flag bits. Resetting them one at a

time allows the host to service them one at a time according to a priority programmed by the user. As in the

MSKI command, bits 1 through 6 of the second (less significant) byte correspond to the potential interrupt

conditions shown in Table 3. Also see description of RDSTAT command. Any zero(s) in this 6-bit field reset the

corresponding interrupt(s). The remaining bits have no effect.

Filter Control Commands

The following two LM628 user commands are used for setting the derivative-term sampling interval, for adjusting

the filter parameters as required to tune the system, and to control the timing of these system changes.

LFIL COMMAND: LOAD FILTER PARAMETERS

Command Code: 1E Hex

Data Bytes: Two to Ten

Data Ranges…

Filter Control Word: See Text

Filter Coefficients: 0000 to 7FFF Hex (Pos Only)

Integration Limit: 0000 to 7FFF Hex (Pos Only)

Executable During Motion: Yes

The filter parameters (coefficients) which are written to the LM628 to control loop compensation are: kp, ki, kd,

and il (integration limit). The integration limit (il) constrains the contribution of the integration term

(2)

(see Equation 1) to values equal to or less than a user-defined maximum value; this capability minimizes integral

or reset “wind-up” (an overshooting effect of the integral action). The positive-only input value is compared to the

absolute magnitude of the integration term; when the magnitude of integration term value exceeds il, the il value

(with appropriate sign) is substituted for the integration term value.

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