MC68HC05V12 Datasheet, PDF (195/246 Pages) Freescale Semiconductor, Inc – HCMOS Microcontreller Unit

Freescale Semiconductor, Inc.
Gauge Drivers
Coil Sequencer and Control
15.7 Coil Sequencer and Control
As shown in Figure 15-15 the digital/analog converter is shared among
all 12 coils. The sequence in which the coils are scanned and the events
that take place during the scanning process are described in this section.
The scan control and status register in 15.7.2 Scan Status and Control
Register controls how the coil sequencer will operate. This register
contains control bits that affect how the gauge sequencer will scan
through the six gauges as well as a status bit to indicate where the
scanning sequencer is in the scanning operation.
15.7.1 Scanning Sequence Description
The coil sequencer can be operated in two basic modes: automatic or
manual. In either mode, each coil is updated by the D/A, muxes, and
sample and hold circuits in the sequence shown in Figure 15-14. One
time through the coil sequence is referred to as a scan cycle. It takes a
time, t_GCS, to update each coil during the scanning sequence. Since
there are 12 coils in the six gauge drivers, it will take a time, 12 * t_GCS,
to complete one scan cycle.
The differences between the automatic and manual modes are
discussed in the following subsections.
15.7.1.1 Automatic Mode
Once all of the coils have been updated, the sequence repeats
automatically. The transfer of data in the CMR and CDRs master-to-
slave buffers is performed at the beginning of each gauge update time.
When one of the coil registers associated with a gauge is written, the
second register also must be written before either value will be used.
The coil registers may be written in either order.
MC68HC05V12 — Rev. 2.0
Gauge Drivers
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Technical Data