M-G362 Datasheet, PDF (24/69 Pages) Epson Company – IMU (Inertial Measurement Unit)

5.10 External Counter Reset Input
The External Counter Reset Input function can be used to measure the time offset from an externally
supplied input trigger on GPIO2(EXT) pin to the completion of the next ADC sampling group.
This function is enabled by writing to EXT_SEL (MSC_CTRL [0x02(W1)] bit [7:6]) to select GPIO2 for
use as an External Counter Reset Input terminal. The active polarity of the input signal (positive
pulse/negative pulse) can be selected by setting EXT_POL(MSC_CTRL [0x02(W1)] bit 5).
The following describes the operation when this function is active:
• The IMU has an internal 16-bit up counter incrementing at 46.875kHz.
• The counter begins counting starting from 0 (*1) when Sampling mode begins.The counting
resolution is approximately 21.33us.
• The counter can be reset by assertion of an external signal on the External Counter Reset
Input terminal. After the counter is reset, the count value is cleared and begins incrementing
again from 0.
• The counter value is transferred at the time of the ADC sampling completion and stored in
COUNT [0x0A(W0)] register before the DataReady signal is asserted.
• The Host can obtain the time offset from External Counter Reset Input signal to ADC sampling
completion time by reading the sampling data with the counter value when DataReady signal
is asserted.
• The counter value is stopped (*2) when Sampling mode is stopped.
• The counter will roll over and increment from 0 again, if the count value increments past
65535.
*1) Enter Sampling mode from Configuration mode
*2) Leave Sampling mode and enter Configuration mode
NOTE: When the External Counter Reset Input function is enabled, the COUNT [0x0A(W0)] register
stores the counter value instead of the sampling count.
The timing specification and timing diagram for the External Counter Reset Input function is shown in
Table 5.2 and Figure 5.10.
Table 5.2 External Counter Reset Input Timing
Parameter
Description
t_ERW
External Reset Input Width
t_ERC
t_ER2A
⊿_ER2A
External Reset Input Cycle
Time from External Reset Input to ADC completion
Precision of t_ER2A
Min
Max
100
-
1
1000
( count^*1 x21.33)+⊿_ER2A
-200
200
*1) The count value is read from register COUNT [0x0A(W0)] as indicated.
Unit
nSec
mSec
μs
μs
20
Seiko Epson Corporation
M-G362PDC1 Data Sheet
Rev.20131217