MC68HC05V12 Datasheet, PDF (197/246 Pages) Freescale Semiconductor, Inc – HCMOS Microcontreller Unit

Freescale Semiconductor, Inc.
Gauge Drivers
Coil Sequencer and Control
Table 15-1. Coil Scanning Sequencer
Coil Number
1
2
3
4
5
6
7
8
9
10
11
12
Coil Name
MAJA1
MAJA2
MAJB1
MAJB2
MINA1
MINA2
MINB1
MINB2
MINC1
MINC2
MIND1
MIND2
Gauge Name
Major A
Major A
Major B
Major B
Minor A
Minor A
Minor B
Minor B
Minor C
Minor C
Minor D
Minor D
Because several CPU write operations may be necessary to write to the
CMRs and CDRs, all of the CMRs and the CDRs contain a master and
a slave buffer to help prevent unwanted fluctuations in coil currents
between the writes to the three registers on a given gauge. Only the
slave buffers will affect the coil currents and direction.
For coil currents to remain as consistent as possible during the scanning
and updating of the gauge coil currents, the sample and hold update
operation must take place in a particular way. The control logic will
perform this function. When the scanning control logic is ready to
advance to the next coil, this operations sequence must take place:
1. Open all sample and hold switches.
2. Increment pointer to next CMR slave register. If both CMRs for this
gauge have been written, transfer new master data to slave buffer
for this CMR and corresponding CDR. If both CMRs have not
been written, don’t transfer data from master to slave.
3. Move slave buffer data to the D/A input.
4. Wait for the D/A output to muxes.
5. Close sample and hold mux and update direction control from
CDR.
MC68HC05V12 — Rev. 2.0
Gauge Drivers
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Technical Data