User`s guide

Code Description
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Controller Configuration for DDCMP
DDCMP makes use of one or more of the general-purpose controller serial lines. To be used for
DDCMP, a serial line must be configured using the Adept CONFIG_C utility program available
in the file CONFIG_C.V2 (for details, see the CONFIG_C documentation in the Instructions for
Adept Utility Programs guide).
DDCMP is available only on global serial ports (i.e., the serial ports on the SIO module, and
ports RS-232-1 and RS-232-2 on the Adept SmartController CX product).
Attaching/Detaching DDCMP Devices
An ATTACH request initiates the DDCMP protocol for the specified logical unit. The attach will
not complete until the remote system also starts up the protocol and acknowledges the local
request. There is no time-out limit for start up, so the attach request can wait indefinitely. For
applications that service multiple lines, no-wait ATTACH mode can be used, and the logical
unit for each line can be polled with the IOSTAT function to detect when the remote system
has started.
A DETACH request stops the protocol, flushes any pending input data, and deactivates the
line. Any data received on the line is ignored.
Input Processing
When the protocol is active, received DDCMP data messages are stored in internal data
buffers and acknowledged immediately. The maximum input message length is 512 bytes.
The total number of data buffers (shared by all the DDCMP serial lines) is initially 10. The
Adept controller configuration program (CONFIG_C) can be used to change the number of
buffers allocated for use by DDCMP.
Once all the DDCMP buffers are full, additional data messages are rejected with negative
acknowledge (NAK) reason #8 (Buffer temporarily unavailable). It is the user's responsibility
to limit the input data flow using a higher-level protocol on the remote system.
Input data is accessed via the V+ READ instruction. Each READ instruction returns the
contents of the next data buffer. If no received data is available, the read will not complete
until a data message is received. No-wait READ mode can be used for reading; the serial line
DDCMP Communication Protocol
V+Language User's Guide, v17.0
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