GE 90-30 PLC, Руководство пользователя

Страница: 48 / 93

4-16 Series 90™-30 PLC LONWORKS® Bus Interface Module User's Manual – June 1997 GFK-1322A
4
Initial Value
This choice allows the user to set the state of the variable upon reset or power-up. When
using hold, the last known value is retained through power-down or reset and this value
is used as the initial state. When the initial state is set to zero, the variable is set to zero
on power-up or reset until changed by normal operation. Use the radio button control to
choose the appropriate initial value.
Bytemap
The bytemap determines the ordering of message bytes when being mapped into register
locations. For standard network variable types the bytemap is predefined and is not
changeable by the user. When defining custom variables, the bytemap will need to be
created in order to assure that the message is placed in the register space in the desired
manner. Please see the section of this manual on defining custom variables.
Saving a Variable Definition
Use the pointer to click on the OK command button in the lower right of the screen to
accept the current variable definition. Clicking OK makes a copy of the definition in the
proper register configuration while the edit copy remains. To continue adding variables
to the current register, simply change the variable name and any of the other fields that
require modification. When finished adding variables to the current register, click on the
cancel command button to return to the register configuration screen. Be sure to save
the current variable definition before leaving the screen.
Message Field
The narrow frame in the bottom left of the screen is a message field. In most cases the
message will show information about the number of register locations available at the
current entry point. For instance, if a variable is being defined with the starting location
0010 and there is a variable defined in location 0015, the space available for the current
variable would be 5. Errors in the definition will cause error messages to appear in this
area.