Motorola GT10 - Manual (Page 147)

GT10/GT30 7.3 GT30 Bit Device Functions
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7.3 GT30 Bit Device Functions
In order for communication to be carried out between the GT30 and PLC, an internal
device area like that shown below is provided in the PLC. This basic communication
area contains two types of devices: word devices, which are used to handle screen
numbers and other data, and bit devices, which are used for bit information. The various
bits of the bit devices are turned on and off from the PLC, and can be used to control
various GT30 operations.
Bit devices
Word position F E D C B A 9 8 7 6 5 4 3 2 1 0
N+0 BZ
Forced–
display flag Backlight
Valid flag Backlight
Flashing Backlight
Color
N+1 Usage prohibited
N+2
BAT
LOW
flag
BAT
Data Input In
Progress flag
Explanation of system areas
BZ ––– This turns on the buzzer.
Forced–Display flag ––– At the rise when the bit is turned on, the screen specified by
the PLC is forcibly displayed. (This is executed only when at the rise of the bit.)
Backlight Valid flag ––– When the bit is turned on, the backlight flashing/backlight
color control becomes effective.
Backlight Flashing ––– 0: Lighted (normal), 1: Flashing
Backlight Color ––– 00: Off, 01: Lighted, 10: Lighted, 11: Lighted
BAT ––– This goes on if clock data and Hold PLC Device data held in the SRAM are
not being backed up normally. (This bit also goes on if the SRAM is not backed up by
the internal secondary battery.)
Data Input In Progress flag ––– This is 1 while data is being input, and 0 when data
input has been completed.
BAT LOW flag ––– This bit goes on if the battery capacitance drops too low. The battery
should be replaced within one week of the time when this bit goes on.
EXPLANATION
DT0 to DT2 and WR0 to WR2 are set as the default values for the basic
communication area.
For information on the contents of all areas of the basic
communication area, please see page 30.
Turning the backlight on and off
The A and B bits of the initial bit device word are used to turn the backlight on and
off. These bits can be changed to change the backlight illumination status.