ProSoft Technology MVI69-S3964R - Manual (Page 57)

Reference MVI69-S3964R ♦ CompactLogix or MicroLogix Platform
Siemens 3964R Protocol
ProSoft Technology, Inc. Page 57 of 80
October 31, 2008
5.2 Functional Overview
5.2.1 Products in the Environment
The 3964R protocol can be installed in all local CompactLogix or MicroLogix
chassis with at least one controller.
You can obtain more information about CompactLogix or MicroLogix and the
CompactLogix or MicroLogix environment through your Rockwell Automation
branch office.
Product Compatibility
The communication between the MVI69 and the CompactLogix or MicroLogix
processor is realized through the module's Input/Output Images.
5.2.2 3964R Protocol Overview
The 3964R Protocol in General
The 3964R protocol defined by Siemens is used for bi-directional data exchange
between two peers through a bit-serial point-to-point connection. This protocol
may be additionally embedded in the RK512 telegram level. If 3964R is used with
RK512, each participant can send jobs to its partner and has read (DB-FETCH)
and write access (DB-SEND) to the partner's data. The data exchange is realized
in the form of messages and response messages. The maximum user data
volume is 512 byte per job and 128 byte per message.
3964R without RK512 allows only block wise sending and receiving of data. The
detailed handshake procedure through messages and response messages is not
applicable in this case.
If both partners want to send a job (3964R with RK512) or data (3964R without
RK512) at the same time, the resulting initialization conflict will be solved through
the high/low priority setup. In such a case one partner will be allocated high
priority and the other one low priority. Thus, in case of an initialization conflict the
device with low priority will defer its job whereas the device with the high priority
will be able to send a job.
The safety of data transmission on the line is guaranteed by a BCC checksum.
You should have sufficient knowledge about the 3964R protocol in order to
understand the operation of the driver for the MVI69-S3964R and to make
efficient use of the example programs.