Command Words for Digital I/O’s Command Mode

There are two command words. First, the command itself is placed on digital inputs 0-15 when the Command Strobe (CPU input 1) is low. Its value is read by the RMC when the Command Strobe transitions high. The second word—the command value or data—is placed on digital inputs 0-15 when the Command Strobe is high and is read by the RMC when the Command Strobe transitions low. Refer to Command Mode for further details on sending the command and command value.

The command given in the command word is not executed until the command value is strobed in (that is, the Command Strobe transitions back low). Commands that request data are an exception; the low 8 bits of the requested data are available as soon as the RMC toggles the Acknowledge bit (CPU output 1). This is done to allow a full 16-bit piece of data to be received in one command cycle.

The following table lists the available commands that can be placed on inputs 0-15:

    1111|11  |    |

Bit#5432|1098|7654|3210

    -------------------

    0AAA|RRRR|0000|0000 No command

    0AAA|RRRR|0000|CCCC Open Loop Using Profile

    0AAA|RRRR|0001|CCCC Set Parameter

    0AAA|RRRR|0010|CCCC Set Profile

    0AAA|RRRR|0011|XXXX Reserved

    0AAA|RRRR|01CC|CCCC ASCII Commands

    0AAA|RRRR|1000|CCCC Go/Set Pressure Using Profile

    0AAA|0000|1001|CCCC Get Parameter

    0AAA|0000|1010|CCCC Get Profile

    0AAA|RRRR|1011|XXXX Reserved

    0AAA|RRRR|1100|XXXX Reserved

    0AAA|RRRR|1101|CCCC Set Parameter On-the-fly

    0AAA|RRRR|1110|00CC Event Step Edit

    0000|0000|1111|0000 Diagnostics

    0001|XXXX|XXXX|XXXX Reserved

    :       :                  :

    1101|XXXX|XXXX|XXXX Reserved

    1110|CCCC|CCCC|CCCC Event Step Transfer

    1111|XXXX|XXXX|XXXX Reserved

Refer to the sections below for descriptions of using each of these types of bits (A, C, R, and X):

A (Axis Select) Bits:

These bits are used to select the axis to which the command is sent and from which the requested data is gathered. Use the following bit patterns to select the desired axis:

Bit #

* Commands to invalid axes are ignored.

C (Command Index) Bits:

These bits are used by the selected command. Refer to the command you wish to use for information on bits marked with C in the chart above.

R (Status Area Request) Bits:

These bits are used to select the data returned in digital inputs 0-7. Refer to the following chart for selecting the data of your choice.

Bit #

* These are 16-bit values. At the time this data is requested, the full 16-bit value is stored in the RMC, and is thus latched. The low byte (bits 0-7) is returned on digital outputs 0-7 after the command word is acknowledged, and the high byte (bits 8-15) is returned on the same outputs after the command value is acknowledged.

† This value returns the In Position and Auto Stop Error bits. An axis In Position bit is set when the bit of the same name in the Status word is set. An axis Auto Stop Error bit is set when an error bit in the Status word is set that has been set to trigger a soft or hard stop using the Auto Stop parameter.

Note: Because commands are not executed until both the command and command data have been received, the In Position bit will reflect the In Position status prior to the command being issued.

After the command word is acknowledged, the In Position bits are put on the eight digital outputs using the following bit positions:

 * This bit is always zero if the axis is not available.

After the command value is acknowledged, the Auto Stop Error bits are returned on the following digital outputs:

 * This bit is always zero if the axis is not available.

X (Don’t Care) Bits:

These bits are ignored.

Copyright (c) 1997-2015 by Delta Computer Systems, Inc.