1. PCI/PCIe TFP Hardware
TFP to retrieve a packet from the GPS receiver. GPS packets that are monitored by the TFP are iden-
tified below.
Packet ID
Monitored
Packet Description
0x41
No
GPS Time
0x42
Yes
Single-Precision Position Fix, XYZ ECEF
0x43
Yes
Velocity Fix, XYZ ECEF
0x44
Yes
Satellite Selection
0x45
No
Firmware Version
0x46
Yes
Health of GPS receiver
0x47
No
Signal Level For All Satellites*
0x48
No
GPS System Message
0x49
No
Almanac Health Page For All Satellites
0x4A
Yes
Single-Precision Position Fix, Lat/Long/Alt
0x4B
Yes
Machine/Code ID And Additional Status
0x4D
No
Oscillator Offset
0x4F
No
UTC Parameters
0x55
No
I/O Options
0x56
Yes
Velocity fix, East-North-Up (ENU)
0x57
No
Information About Last Computed Fix
0x5E
No
Additional Fix Status
0x83
No
Double-Precision Position Fix, XYZ ECEF
0x84
No
Double-Precision Position Fix, Lat/Long/Alt
* Note: The first byte returned will be the length of the packet.
The retrieve packet command works as follows:
n
If the requested packet is being monitored and a local copy exists, then the TFP transfers its local
copy of the packet to the DPRAM GPS Packet Area, sets ACK bit 2, then sets ACK bit 0 to
acknowledge the retrieve packet command.
n
If the requested packet is not being monitored or if the TFP has not yet received a monitored
packet, then the TFP must request the packet from the receiver by sending the appropriate
request packet. Once the request has been sent, the TFP sets ACK bit 0 to acknowledge the
retrieve packet command. Later, when the receiver responds with the retrieved packet, the TFP
transfers the packet to the DPRAM GPS Packet Area and sets ACK bit 2. If the receiver does not
respond to the request within a timeout period (typically 3 seconds), then the TFP sets the packet
length byte in the DPRAM GPS Packet Area to zero and sets ACK bit 2.
n
If the retrieved packet ID is not on the list above, the TFP sets the packet length byte in the
DPRAM GPS Packet Area to zero, sets ACK bit 2, then sets ACK bit 0.
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