33813 Datasheet, PDF (30/54 Pages) Freescale Semiconductor, Inc – One Cylinder Small Engine Control IC

Table 11. SPI VRS Manual Configuration Register
SPI VRS Manual Parameters Configuration Register
Bits 7, 6, 5, 4
Threshold Values (nominal)
0100
0101 (default)
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
23 - 55 mV
(Tolerance not specified below 110 mV threshold. Only specified for monotonicity.)
35 - 75 mV
(Tolerance not specified below 110 mV threshold. Only specified for monotonicity.)
74 mV
(Tolerance not specified below 110 mV threshold. Only specified for monotonicity.)
110 mV - 1.715 V +/- 20%
150 mV +/- 20%
215 mV +/- 20%
300 mV +/- 20%
425 mV +/- 20%
600 mV +/- 20%
850 mV +/- 20%
1.210 V +/- 20%
1.715 V +/- 20%
5.1.23 Controls for the VRSN and VRSP Inputs
The VRS can be connected to the 33813 in either a differential or single-ended fashion. The use of differential filtering capacitor,
and grounded capacitors of at least 100 nF are also advisable. In some applications, a damping resistor of approximately
5.0 kOhm directly across the pickup coil is also useful to minimize high frequency ringing.
5.1.24 GND VRSN Bit
To use the VRS inputs in a single-ended configuration the “GND VRSN” bit in the SPI Configuration register must be set to indi-
cate to the 33813 that this mode is being used. The VRS is then connected between the VRSP input and ground. The default for
this bit is zero (0) indicating that the differential mode is selected.
5.1.25 2.5 Volt Reference Disconnect Bit
The disconnect 2.5 Volt reference bit in the SPI VRS configuration register is used to disconnect the internal 2.5 Volt reference
signal from the VRSN and VRSP inputs, so that an external reference voltage can be employed. The default state of this bit is
zero (0), indicating that the internal 2.5 Volt reference voltage is connected to the VRSN and VRSP inputs.
5.1.26 Selecting the Input Threshold and Blanking Time
Two different SPI registers are provided to control the VRS circuit values in the manual mode. The SPI VRS configuration register
is used to set the “engine running” values for the threshold and blanking filter and the SPI VRS control register is used to provide
the “engine cranking “threshold and blanking filter values. Once the engine is running, the MCU clears the SPI VRS control
register and the 33813 will use the values found in the SPI VRS configuration register.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33813
30