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1、 1PPS OutBy default, the receiver generates a TTL-level pulse every second within one microsecond of the GPS time for synchronization of external equipment. Refer to your individual receiver manual to determine signal location on the pinouts of the ports. This pulse can be offset using the $PASHS,PP
2、S command (refer to “PPS: Pulse Per Second” on page 122). It can also synchronize either the rising edge(default) or the falling edge to the GPS time. The receiver can generate this signal with a different period (0.1 to 60 seconds). Setting the period to 0 disables the PPS pulse.You may output the
3、time tag of the pulse to a serial port via the$PASHS,NME,PTT,c,ON (where c is the output port). This message will be sent within 100ms of the pulse. It has been designed to minimize the latency when the offset is 0.0 (within 30ms of the pulse when Fast CPD is off).This output is driven by a 3.3 volt
4、 CMOS gate through a 150 ohm resistor, and is intended to drive a high-impedance TTL or CMOS input. The minimum allowable input resistance to guarantee TTL input levels is 250 ohms. PPS: Pulse Per Second$PASHS,PPS,d1,f2,c3The receiver generates PPS pulse with programmable period and offset with resp
5、ect to GPS time. The PPS set command allows the user to change the period and the offset of the pulse, and to either synchronize the rising edge of the pulse with GPS time, or synchronize the falling edge of the pulse with GPS time. PPS is generated by default once every second with its rising edge
6、synchronized to GPS time and no offset. Table 6.39. PPS Message StructureParameterDescriptionRangeUnitsd1period0-60Secondf2offset999.9999Millisecondsc3rising edge or falling edgeR / Fn/aThe period set to 0 will disable the PPS output. Between 0 and 1, the period can be set in increments of 0.1. Betw
7、een 1 and 60, the period can be set in increments of 1.122Z-Family Technical Reference ManualExample: Set PPS to a period of 2 seconds, a offset of 500ms, and synchronize the rising edge of the pulse with GPS time.$PASHS,PPS,2,+500,R $PASHQ,PPS,cQuery PPS parameter where c is the output port. Note t
8、hat c is not required to direct the response message to the current communication port.Example: Query PPS parameters to port A.$PASHQ,PPS,A $PASHR,PPSThe response is in the form:$PASHR,PPS,d1,f2,c3*cc where Table 6.40 outlines the structure: Table 6.40. PPS Response StructureParameterDescriptiond1Pe
9、riod. Range from 0 to 60.0f2Offset, Range from -999.9999 to +999.9999c3Edge, R = rising edge or F = falling edgeccChecksumPTT: Pulse Time Tag Message$PASHS,NME,PTT,c,s,fEnable/disable output of PPS pulse time tag message, where c is the output port, s is ON or OFF, and f is the optional output rate
10、parameter in seconds. If the output rate is not set, the command is output at the rate set by the$PASHS,NME,PER command.The reponse message is output as soon as possible after the PPS pulse isCommands225generated (with minimum latency, 50 ms if PPS offset is 0, otherwise 150 ms), and contains the GP
11、S time at which the latest PPS was sent, including the offset if an offset was set when the PPS pulse was enabled.The period of the PTT message is independent of the NMEA period. It is only linked to the PPS period.Example: Enable PTT message on port A:$PASHS,NME,PTT,A,ON $PASHQ,PTT,cQuery the time
12、tag of the next PPS pulse, where c is the optional output port. If c is not specified, the reply is sent to the port on which the query was made.The response will be sent out once, right after the next PPS pulse is generated, and contains the GPS time at which the PPS pulse was sent, including the o
13、ffset if an offset was set when the PPS pulse was enabled. Thus the response may be delayed by one PPS period plus the time tag latency indicated above.$PASHR,PTTThe PTT response message is in the form:$PASHR,PTT,d1,m2*cc where the message structure is as defined in Table 6.124. Table 6.124. PTT Mes
14、sage StructureParametersDescriptionRanged1Day of GPS week,1 to 7, Sunday = 1m2GPS time in hours, minutes, seconds of thePPS pulse hh:mm:ss.sssssss0 -23:59:59.9999999Typical PTT response message:$PASHR,PTT,6,20:41:02.0000000*OD Table 6.125 describes a typical PTT response message. Table 6.125. Typical PTT Response MessageItemDescription6Day of week (Friday)20:41:02.0000000GPS Time (8:41:02 PM)*ODMessage checksum in hexadecimal
