PNI RM3000 Sensor Suites - Manual (Page 36)

PNI Sensor Corporation Doc #1015673 r08
RM3000 & RM2000 Sensor Suite User Manual – July 2012 Page 36 of 41
6 3D MagIC Operation
– Legacy Mode
Note: This section discusses how to operate the 3D MagIC in Legacy Mode. For a description of
operation in Standard Mode, see Section 5. The 3D MagIC will operate in Legacy Mode when pin #12 is
held HIGH (connected to DVDD).
The intent of Legacy Mode is to enable the user to easily substitute PNI’s 3D MagIC for PNI’s
legacy 11096 ASIC (p/n 12576).
If the user wishes to simply duplicate the performance of the 11096 ASIC (Legacy Operation),
then a measurement is made by sending the Legacy Command Byte. This command byte is the
same as for the 11096 ASIC. The Legacy Command Byte initiates a sensor measurement on a
single sensor, and sets up the 3D MagIC to output the measured values on the MISO line.
Legacy Operation is covered in Section 6.1
If the user wishes to derive the lower power consumption advantages of the 3D MagIC and is
willing to make some code changes but cannot make hardware changes, then Enhanced Legacy
Operation allows for this. (If the user can make both code and hardware changes, then operation
in Standard Mode is recommended.) For Enhanced Legacy Operation, the user first will write to
the Clock Divide Register and after this follow the same process as for Legacy Operation.
Please review both Sections 6.1 and 6.2, as Section 6.1 still applies and Section 6.2 covers the
additional steps required for Enhanced Legacy Operation.
6.1 Legacy Operation
In Legacy Mode a sensor measurement is initiated with the Legacy Command Byte, and this
command also sets up the 3D MagIC to output measurement data on the MISO line once this
data becomes available.
Note the 3D MagIC’s high-speed clock runs at nominally 45 MHz, but the 11096 ASIC runs
at nominally 2 MHz. Consequently, when the 3D MagIC is in default Legacy Mode, the
clock speed is divided by 16 thus reducing the clock speed to 2.8 MHz. At an effective clock
speed of 2.8 MHz the gain of the 3D MagIC circuit will closely match the gain of the 11096
ASIC circuit operating at 2 MHz. (The effective clock speed of the 3D MagIC is not 2 MHz
for gain matching because of differences in the circuit oscillation frequency between the 3D
MagIC and the 11096 ASIC circuits.) As such, the performance of the 3D MagIC closely
matchs that of the 11096 ASIC circuit with no software coding or hardware changes on the
user’s part. But performance is sub-optimized, and specifically power consumption can be
reduced by up to 90% with software changes on the user’s part, as discussed in Section 6.2.