ComNav P4 - Speed Mode and Timing Outputs

ComNav P4 Installation and Operation
Document PN 29010100 V1r0 - 65 -
Speed Mode and Timing Outputs
The P4 SPU outputs two status signals on the J12 – MISCELLANEOUS connector. The
receptacle is supplied with a 10-pin mating plug.
In addition, a 1 pulse per second (PPS) timing signal is output on J12. It is about 5%
accurate, and is meant for general-purpose use. For example, some brands of Radar and
other navigation equipment require a “1 PPS” timing signal for proper operation.
These two status signals indicate:
 If the system is operating with the Hi or Lo speed steering parameters in effect,
in AUTO or NAV modes
 If the system is operating in WORK mode
The status signals are meant to be used to allow indication of those conditions on an external
alarm or indicator. While both conditions are indicated on the Control Head’s LCD display, but
it is also sometimes useful to have them alert with an external alarm or lamp at locations other
than where the Control Head is located.
These two outputs can also be used to control automatic deployment (and retrieval) of
external “stabilizer” equipment, to enhance the vessel’s steering and stability when it is
moving at a slow speed, or when WORK mode is in effect. In both these situations, the boat is
moving slowly, and so there is not as much steerageway (i.e., less water flowing over the
rudder, so it does not generate as much sideways force).
All three outputs are logic-level, open-drain outputs direct from the SPU’s microcontroller,
and must be used only within the following voltage/current limits:
 Each output requires its own external pull-up resistor, which must be wired only
to the SPU’s logic power supply (5 VDC, created by a linear regulator on the
SPU, and available at the V+ pin of J12), and to the external alarm, lamp and/or
control circuit. The resistor value plus the impedance of the load must total no
less than 3K3 Ohms (to limit the current into the pin in the “0 V” state to less
than 1.6 mA).
 If needed, the SPU’s ground reference for these signals is on the GND pin of J6.
Signal
J12 Pin
When at 0 V
When Open-circuit
WORK MODE
WORK
Normal mode
WORK mode engaged
SPEED MODE
HI SPD
Lo Speed
Hi Speed
1PPS
1PPS
(1 pulse per second, ~50% duty cycle)
Table 2 – Speed Mode and Timing Outputs
All outputs are ESD-protected – but you still must use them with care:
 Do not use more than about 0.5 m of cable to connect them to the external
alarm/indicator or stabilizer-control circuit.
 If you must connect to something farther away than that, use a suitable buffer or
isolator circuit – a transistor, a relay or (preferred) an opto-isolator block. With a
relay, be sure to wire a flyback-suppressor diode across the coil.
 If shielded wire is used, connect the shield only at the SPU – to the GND pin of J6.
Note: unused pins on J12 are reserved for possible future use.
Installation