LM628, LM629

SNVS781C – JUNE 1999 – REVISED MARCH 2013

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User Command Set

GENERAL

The following paragraphs describe the user command set of the LM628. Some of the commands can be issued

alone and some require a supporting data structure. As examples, the command STT (STarT motion) does not

require additional data; command LFIL (Load FILter parameters) requires additional data (derivative-term

sampling interval and/or filter parameters).

Commands are categorized by function: initialization, interrupt control, filter control, trajectory control, and data

reporting. The commands are listed in Table 2 and described in the following paragraphs. Along with each

command name is its command-byte code, the number of accompanying data bytes that are to be written (or

read), and a comment as to whether the command is executable during motion.

Initialization Commands

The following four LM628 user commands are used primarily to initialize the system for use.

RESET COMMAND: RESET THE LM628

Command Code: 00 Hex

Data Bytes: None

Executable During Motion: Yes

This command (and the hardware reset input, Pin 27) results in setting the following data items to zero: filter

coefficients and their input buffers, trajectory parameters and their input buffers, and the motor control output. A

zero motor control output is a half-scale, offset-binary code: (80 hex for the 8-bit output mode; 800 hex for 12-bit

mode). During reset, the DAC port outputs 800 hex to “zero” a 12-bit DAC and reverts to 80 hex to “zero” an 8-bit

DAC. The command also clears five of the six interrupt masks (only the SBPA/SBPR interrupt is masked), sets

the output port size to 8 bits, and defines the current absolute position as home. Reset, which may be executed

at any time, will be completed in less than 1.5 ms. Also see commands PORT8 and PORT12.

PORT8 COMMAND: SET OUTPUT PORT SIZE TO 8 BITS

Command Code: 05 Hex

Data Bytes: None

Executable During Motion: Not Applicable

The default output port size of the LM628 is 8 bits; so the PORT8 command need not be executed when using

an 8-bit DAC. This command must not be executed when using a 12-bit converter; it will result in erratic,

unpredictable motor behavior. The 8-bit output port size is the required selection when using the LM629, the

PWM-output version of the LM628.

PORT12 COMMAND: SET OUTPUT PORT SIZE TO 12 BITS

Command Code: 06 Hex

Data Bytes: None

Executable During Motion: Not Applicable

When a 12-bit DAC is used, command PORT12 should be issued very early in the initialization process. Because

use of this command is determined by system hardware, there is only one foreseen reason to execute it later: if

the RESET command is issued (because an 8-bit output would then be selected as the default) command

PORT12 should be immediately executed. This command must not be issued when using an 8-bit converter or

the LM629, the PWM-output version of the LM628.

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