Rockwell Automation 1785-Vx0B, D17856.5.9 PLC-5 VME VMEbus Programmable Controllers User Manual User Manual
Page 21
Chapter 1
Overview
1-10
Table 1.B
Comparison of 6008-LTV and PLC-5/VME Processor Attributes
Attributes
6008-LTV
PLC-5/VME
Comments
VME slots
3
2
Bus arbitration
No
Yes or No (user configurable)
Single level arbiter
VME master
Yes
Yes
VME Slave
Yes
Yes
Global memory (bytes)
1
1K short, 4K short or standard
64K standard
Global memory is selectable
Programming and downloading
over backplane
No
Yes
With 6200 series software
release 4.4 and later
Saving over backplane
No
Yes
With 6200 series software
release 4.5 and later
PLC
data table to global memory trans-
fer method
Continuous-copy command
Continuous-copy and/or ladder
MSG commands
Asserts VME SYSFAIL
Yes
Yes
PLC resets upon VME SYSRESET
Yes
Yes
Bus request line
0, 1, 2, 3
1, 3
Bus release
ROR, RWD, ROC
ROR, RWD, ROC
Continuous-copy command file size
500 words
1000 words
Ladder MSG file size
N/A
1000 words
RS-232 port
No
Yes
Remote I/O baud rate
57.6k baud fixed
57.6k, 115.2k, 230.4k baud configurable
Remote I/O fractional rack addressing
No
Yes
1
All of the 6008-LTV’s global memory could be configured to be totally within short memory. Because the PLC-5/VME processor’s global memory would totally fill all of
VME short memory, it can only be selected with a standard memory address. This may be a consideration when replacing a 6008-LTV with a PLC-5/VME processor.
There are some areas of potential incompatibility to consider:
The configuration/control/status/message registers are slightly different,
requiring changes to the host driver program.
The LTV VME global memory can be selected to be in short or standard
memory space. The PLC-5/VME processor’s global memory can only
be selected to be in standard memory. Because of this, the 6008-LTV
will accept address modifiers 2D, 3D 29 and 39. The PLC-5/VME
processor will only respond to address modifiers 3D.
The 6008-LTV supports logical rack address 0; the PLC-5/VME
processor does not.
The 6008-LTV has a status/configuration bit to enable or ignore ROC
(release on clear). The PLC-5/VME processor will always respond
to ROC.