32
8. OPERATION AS A CLOCK
When configured as a clock the BA578E can display
local time in a variety of twelve or twenty four hour
formats.
The displayed time can be adjusted via
the front panel push buttons which may be protected
by a user definable four digit security code to
prevent unauthorised or accidental adjustment.
The clock may be synchronised to an external time
standard via the instrument's reset terminals. When
these two terminals are connected together by an
external switch contact, the clock display will be
reset to a preconfigured time and will resume
running from this time when the contacts are
opened.
The optically isolated status open collector output
can be used to monitor the clock or to perform
simple control functions.
When fitted with the optional galvanically isolated
control outputs the clock can be configured to turn
each solid state output
on
and
off
twice during each
twenty four hour period.
Fig 13 shows a simplified block diagram of the
BA578E configured as a clock.
The instrument can be supplied with the following
factory fitted accessories:
Backlight Internally powered
Dual isolated control outputs
Fig 13
BA578E block diagram with clock
configuration.
8.1
Initialisation and loss of power
Each time power is applied to a BA578E
initialisation is performed. After a short delay the
following display sequence occurs:
All segments of the display are activated
Instrument starts functioning, using the
configuration information stored in the
instrument's permanent memory.
Following initialisation, the instrument will have a
flashing display which is a request for the local time
to be entered.
The clock will not start to function
until a display time has been entered, or the remote
reset
contacts
are
closed
and
opened
to
synchronise the clock to a preconfigured time.
If during normal operation the power supply is
interrupted for more than 30ms, the display will
return to the flashing condition and the display time
will have to be re-entered.
This time may be
increased by powering the Clock from a lightly
loaded
instrument
supply
with
large
output
capacitance.
8.2
Controls when configured as a clock
The BA578E clock is configured and adjusted via
four front panel push buttons. In the display mode
i.e. when the instrument is displaying time, the push
button functions are:
Push Button Functions
(
+
&
Shows firmware version
(
+
)
Access to configuration menu
Note:
When optional control outputs are fitted, the
BA578E clock may be configured to provide direct
access to the control outputs from the display mode
when the
(
and
*
push buttons are operated
simultaneously. - see section 8.4.16
8.3
Displays when configured as a clock
The BA578E clock has a single digital display plus
annunciators.
Time
Shows time in selected 12 or
display
24 hour format.
Reset
Activated while clock is being
annunciator
synchronised and external
reset contacts are closed.
Status output
RTx shown while status
annunciator
output is activated.
Control output
Show status of both optional
annunciators
control outputs.
