PNI RM3000 Sensor Suites - Manual (Page 37)

RM3000 & RM2000 Sensor Suite User Manual r08 Page 37 of 41
6.1.1 Legacy Operation SPI Activity Sequence
The SPI activity sequence is given below for Legacy operation. SPI timing is discussed
in Section 4.4. The Return Byte is 9B
H
. Two (2) data bytes will be clocked out for a
Legacy measurement. The Command Byte is discussed below.
Figure 6-1: SPI Activity Sequence Diagram for Legacy Operation
6.1.2 Legacy Command Byte
The command byte to initiate a sensor measurement is defined as follows:
Bit # 7 6 5 4 3 2 1 0
Value 0 PS2 PS1 PS0 0 0 AS1 AS0
PS0-PS2: Period Select
Selects the number of sensor circuit oscillation cycles (cycle counts) to be counted
while simultaneously using the internal fixed reference clock to measure the time to
obtain this count.