PNI CompassPoint V2Xe - Manual (Page 9)

PNI Sensor Corporation DOC#1017814 r01
V2Xe User Manual – May 2012 Page 7
Figure 4-1: Transfer from Host to V2Xe
Figure 4-2: Transfer from V2Xe to Host
The nature of the SPI interface is such that the host receives the bytes synchronously while
sending bytes. Therefore the V2Xe will send a byte containing 0x00 for every byte received.
The V2Xe itself will ignore any bytes received while it is sending a response. When the host
keeps clocking the SPI interface after the V2Xe has completed sending a response, the V2Xe
will keep sending 0x00 for each byte clocked out. In effect, the connection is made to act
like a half duplex connection. The host sends a request and the V2Xe responds (if
applicable).
The V2Xe has a built-in transmit response timeout. If the host sends a query command to the
V2Xe, the host needs to clock in the response within 0.5 seconds. The V2Xe will flush the
response after the 0.5 second timeout to accommodate new commands.
SSN
SSN
*Tri-state when SSN is HIGH.
*Transmit zero-byte (recommended)
**Tri-state when SSN is HIGH.