Seiwa SW AP03 User Manual

Page 47

Data format and sentences to comply with NMEA0183 V3.00
Serial data format:

Baud Rate 4800
Character format: start bit, 8 data bits, LSB first

MSB (bit 7) = 0, no parity bit,
1 or 2 stop bits

Polarity

Idle, stop bit,logic'1' Line A < 0.5V above line B.
Start bit, logic '0' Line A > 4V above Line B.

INPUT PORT(S) Isolated via optocoupler

Input resistance 1000 ohm min.

OUTPUT PORT Non-isolated differential output

Output voltage 18 V p-p (typical)
Source resistance 1500 ohm max

AUTOMATIC SENTENCE SELECTION
For navigation inputs, the system looks for groups of sentences in this order:

RMB and RMC

RMB and GLL

APB and GLL
APA and GLL

BOD and XTE

The search stops on the first complete group. If only one sentence is found from the
above combinations, the autopilot operates from the data in that sentence.

For wind vane inputs, the system looks for sentences in this order:

MWV

VWR

Note: that the MWV sentence should contain the symbol R
following the w ind angle field.

For a digital heading input, the system looks either for the HDG or HDT sentence,
depending on w hich one is selected in the Menu 3 option. Variation and deviation
fields are not read.

OUTPUT DATA
The system outputs heading data in either the IIHDG sentence (without deviation or
variation data) or as IIHDT, using the magnetic variation set within the autopilot. The
repetition rate is a minimum of 8 per second.