I'm getting what appears to be more requests for hot backup using Allen Bradley PLC and SLC platforms. I have my own opinion regarding the need for this but I'm curious what the collective school of thought is from the experts here at this site.
AB has different solutions to redundant processors, depending on the platform and communications protocol chosen. In the SLC line, the 1747-BSN module lets you switch RIO or DH+ to the active processor along with the RS232 link for an LOI. In the PLC line, the 1785-BCM gives you the same functionality. All this works well as long as the LOI is using DH+ or serial links since the backup module handles the redirection and no addressing changes are involved.
However, when using controlnet backup with the PLC line, the controlnet address of the two processors is different, so the LOI can't easily switch to the active processor when transfer occurs. The exact same problem exists with Ethernet on either processor line. How have you gotten around this? And is anybody really doing much hot backup these days?
Sorry for such a long winded question. The local AB folks haven't been able to give me very firm guidance on this either.
AB has different solutions to redundant processors, depending on the platform and communications protocol chosen. In the SLC line, the 1747-BSN module lets you switch RIO or DH+ to the active processor along with the RS232 link for an LOI. In the PLC line, the 1785-BCM gives you the same functionality. All this works well as long as the LOI is using DH+ or serial links since the backup module handles the redirection and no addressing changes are involved.
However, when using controlnet backup with the PLC line, the controlnet address of the two processors is different, so the LOI can't easily switch to the active processor when transfer occurs. The exact same problem exists with Ethernet on either processor line. How have you gotten around this? And is anybody really doing much hot backup these days?
Sorry for such a long winded question. The local AB folks haven't been able to give me very firm guidance on this either.