VMIC / GE Fanuc VMIVME-2540 User Manual

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VMIVME-2540 Intelligent Counter/Controller

Command Descriptions

The following sections describe the command codes and the usage of the command codes for performing the operations supported by the VMIVME-2540 module.

The required front panel connections are also described for each of the commands that require an input signal, or the use of an output signal connection for proper channel operation.

Initialization and Synchronization Command Codes

A portion of the command codes provide for the initialization of the VMIVME-2540 and individual channels. An additional command provides the host program with the capability to initialize the command status prior to writing the command. Command status interrogation provides the primary synchronization mechanism with the

VMIVME-2540 for the host program.

Command $00:

Disable Channel. The disable channel command instructs the

VMIVME-2540 local CPU to disarm the counter(s) associated with the currently active command for the selected channel. The CCB(s) contents for the selected channel is cleared (set to zeros). This command must be issued by the user for any active channel before commanding any mode of operation. If the user commands a mode of operation for an already active channel, the VMIVME-2540 local CPU returns the

active channel error command status code. The disable channel command may be issued to any channel configured for 16-bit operation. A channel pair configured for

32-bit operation must be disabled by issuing the disable channel command to the lower (even) channel number. The QPC operation must be disabled by issuing the disable channel command to the lowest (even) channel of the four-channel group. If the user issues the disable channel command for other than the correct channel for an active multichannel operation, the VMIVME-2540 local CPU reports the channel

allocation error status code. A disable channel command can be sent for an inactive

(disabled) channel, and a normal command acknowledge command status will be returned to the host processor.

Command $1B:

Initialize. This command instructs the VMIVME-2540 local CPU to initialize all shared memory variables and AM9513A system timing controllers to the same state as that which immediately follows self-test from powerup or front panel reset. All channels are disabled, channel outputs are set to zero, and all channel CCBs are cleared. The initialize command requires only milliseconds to execute and is appropriate for execution when a host program restart is initiated.

Command $1C:

Reset Command Status Buffer. This command instructs the

VMIVME-2540 local CPU to write $xx00 to the command status buffer, located at offset $0006 from the base address. As noted in the command status buffer description, the upper byte of the command status buffer is undefined, while the lower byte is cleared by this command. The response time for this command is less than 50 µs. This command provides the necessary synchronization with the

VMIVME-2540 local processor when polling is used to transfer commands. Proper command-to-command status sequencing requires that the reset command status command be issued first, then the command status buffer be verified for a zero value.

The desired operational command is then issued to the VMIVME-2540, and a command status is verified by reading a nonzero status, followed by a second read which is verified to match the previous nonzero read. This loop should be repeated

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