1756-EWEB Module: Web Server and More - Rockwell Automation

105. Click the See message you are going to send button again and make sure that a
smaller message is displayed in the popup.
106. Click OK.
107. Click the Send to Instructor button.
108. Click OK on the dialog that confirms the message has been sent. Your message
should arrive in your instructor’s inbox momentarily.
Why the EWEB does not replace the PanelView Plus
• The EWEB is a single threaded Web server, it cannot do high speed data
collection. This is intentional, so that control system performance is not
compromised by the presence of the EWEB.
• All the tag names have to be known in order to read or write them. All the
benefits of FactoryTalk Directory Direct Tag Referencing are lost.
• There is no simple HMI graphics editor that allows you to drag and drop objects
onto screens. Any graphic HMI pages would have to be written as web pages.
• Web pages need to be refreshed. This effect is virtually non-existent with HMIs.
• There is no Alarming or Unsolicited data from the EWEB.
• Data Views can access only Controller Scoped Tags, and only tags of type
BOOL, SINT, INT, DINT, REAL or STRING. Custom Web pages do not have
these limits.
• Only 2500 tags can appear in all Data Views combined, but there is no limit to the
number of Data Views or the number of tags per Data View, except for the 2500
total tag limit. Custom Web pages do not have these limits.
• Quick and Dirty Simple Summary: HMI: Allows you to look at lots of data
locally. EWEB: Allows you to look at a limited amount of data from anywhere.
LAB 1: 1756-EWEB Module
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