MC68HC05V12 Datasheet, PDF (191/246 Pages) Freescale Semiconductor, Inc – HCMOS Microcontreller Unit

Freescale Semiconductor, Inc.
Gauge Drivers
Gauge Driver Control Registers
The theoretical current that will flow between the + and − pins is given by
this equation:
I = _{(}ICM)X_^{R-----e---g-2---5-v---5a----l-u---e--}_{}
I_CM is the maximum current that can be driven into any of the coil drivers
and is given by this equation:
I_CM = (I_MAX x 10) x (1 + E_CA + E_MAX)
E_CA is the total internal error in generating I_CM from I_MAX and is shown
in 17.11 Gauge Driver Electricals.
The E_MAX is the error tolerance of the R_MAX resistor and is shown in
17.11 Gauge Driver Electricals.
The “reg value” is the base 10 representation of the value written to the
magnitude registers.
I_MAX is set by the external resistor and is a reference current that is used
to generate the coil currents.
I_MAX is related to the external R_MAX resistor by the equation:
I_MAX = _(R2M^.5_{AX ) x 4}
15.6.3 Current Direction Registers
The bits in these registers control the direction of current flow in each of
the full eight H-bridge drive outputs. Note that only coil 2 in the minor
gauges requires a direction bit. Since coil 1 in each of the minor gauges
is a half H-bridge driver, it only requires a current magnitude register.
The CDR also contains a master and slave latch. A read of any of these
registers will return the value in the slave buffer.
MC68HC05V12 — Rev. 2.0
Gauge Drivers
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Technical Data