GE Industrial Solutions MX150_MX250 Modbus Network Card - Manual (Page 6)

■ ■ 4 GE Zenith Controls ■ ■ MX150/MX250 Series Modbus Network Card (71R-2200)
Operation
Setting System Time
Holding Registers 40094 through 40099 are provided to
control and report the status of the controller’s System
Time. Reading Holding Register 40094 through 40099
will report the current Hour, Minute, Day, Month, Year,
and Day of Week to which controller’s internal clock is
currently set.
Writing the System Time Holding Registers
Holding Registers 40094 through 40098 must be written
using a Write Multiple Holding Register Command
(Function Code 16). This is to ensure that the data con-
tained in these registers is a complete ordered set. Any
attempt to write Holding Registers 40094, 40095, 40096,
40097, or 40098 with a Write Single Holding Register
Command (Function Code 6), or a Write Multiple
Holding Register Command (Function Code 16) that
does not include the entire range of 40094 - 40098, will
result in an Illegal Data Address exception response
from the Modbus Card.
Note: Holding Register 40099, “System Time-Day of
Week” is Read Only. The value of this register is auto-
matically computed and updated by the controller,
based on the calendar date.
Operation with In-Phase Monitor
Special consideration is required if the controller is con-
figured with the In-Phase Monitor. Most Modbus net-
work data and control are unavailable while the In-Phase
Monitor is waiting for phase synchronization. The
Modbus Network Card will return a “Slave Device Busy”
exception code (06h) to all Modbus queries, except for
queries to the System Busy Status Register (Holding
Register 40112) or the System Busy Control Register
(Holding Register 40113).
If the Modbus Network Card returns a Slave Device Busy
exception code, information about the source of the
busy condition may be available in the System Busy
Status Register (Holding Register 40112). If Bit 0 of the
System Busy Status Register (Coil 105) is set to one, the
controller is busy waiting for phase synchronization.
If the controller is busy waiting for phase synchroniza-
tion, the In-Phase Monitor may be bypassed over the
Modbus network by performing the following sequence:
Warning: EXTREME CAUTION must be used when
bypassing the In-Phase Monitor! Transferring between
sources that are not in phase synchronization may cause
unexpected operation, resulting in damage to plant
equipment and personnel.
1. Set Bit 0 of the System Busy Control Register (Coil
113) to one. This is a request by the Modbus user to
bypass the In-Phase Monitor.
2. Once an In-Phase Monitor bypass has been requested,
and the controller has been waiting for phase synchro-
nization for more than one minute, the controller will
request confirmation of the In-Phase Monitor bypass.
This request is indicated by a one in Bit 1 of the System
Busy Status Register (Coil 106).
3. To confirm the request to bypass, set Bit 1 of the
System Busy Control Register (Coil 114) to one.
The controller will bypass the In-Phase Monitor.
Note: The In-Phase Monitor bypass feature is an inter-
locked command-and-confirm mechanism. The Modbus
Card will not allow the Confirm Bypass control bit
(Coil 114) to be set before the controller has set Ready
to Confirm Bypass status bit (Coil 106). If a write request
is received to set Coil 114 before the controller has set
Coil 106, an Illegal Data Value error code will be returned.
Bypass Pending Exerciser
Bit 0 (Coil 121) is the Bypass Pending Exerciser bit.
The MX Platform performs a logic-OR with this bit and
the BPASS EXER key on the HMI. A 1 in Bit 0 bypasses
the pending exerciser; a 0 does nothing.
Cancel Bypass
Bit 1 (Coil 122) is the Cancel Bypass bit. The MX
Platform performs a logic-OR this bit with the CANCL
BPASS key on the HMI. A 1 in Bit 1 cancels the Bypass
Pending Exerciser. A 0 in this bit position does nothing.
The Bypass Pending Exerciser Bit works different,
between a Timer Exerciser and Clock Exerciser,
depending on the state of Exerciser Type (Holding
Register 40063, Bit 0, Coil 81). When Coil 81 = 0 (Timer
Exerciser), if Coil 121 is set to 1, the Timer Exerciser
will be bypassed until the Cancel Bypass Bit (Coil 122)
is set to 1. When Coil 81 = 1 (Clock Exerciser), if Coil
121 is set to 1, only the exerciser that is pending at the
time gets bypassed, and the exerciser only gets bypassed
once. The Controller waits for Coil 121 to reset to a 0
before a subsequent bypass can be performed.
Operation Under Battery Backup
The controller can be powered from an external 12-volt
battery in the event that neither S1 nor S2 are available.
While the controller is on external battery backup,
data will still be available over the Modbus Network
as noted below.
While the controller is running on external battery
backup, data regarding ATS position and limit switch
inputs may be invalid if both S1 and S2 sources are lost.
Therefore, if Bits 6 and 7 of Holding Register 40001,
or Coils 7 and 8, are both zero, the following Modbus
network data may not be reliable:
• Automatic Transfer Relay –
Holding Register 40001, Bit 0 or Coil 1
• SN Limit Switch –
Holding Register 40002, Bit 0 or Coil 9
• SE Limit Switch –
Holding Register 40002, Bit 1 or Coil 10
• SNO Limit Switch –
Holding Register 40002, Bit 2 or Coil 11
• SEO Limit Switch –
Holding Register 40002, Bit 3 or Coil 12
• S1 Position Status –
Holding Register 40004, Bit 9 or Coil 34
• S2 Position Status –
Holding Register 40004, Bit 10 or Coil 35