HPC16064 Datasheet, PDF (22/36 Pages) National Semiconductor (TI) – High-Performance microController

MICROWIRE PLUS (Continued)
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FIGURE 24 MICROWIRE PLUS
MICROWIRE PLUS Operation
The HPC46064 can enter the MICROWIRE PLUS mode as
the master or a slave A control bit in the IRCD register
determines whether the HPC46064 is the master or slave
The shift clock is generated when the HPC46064 is config-
ured as a master An externally generated shift clock on the
SK pin is used when the HPC46064 is configured as a slave
When the HPC46064 is a master the DIVBY register pro-
grams the frequency of the SK clock The DIVBY register
allows the SK clock frequency to be programmed in 14 se-
lectable binary steps or T3 underflow from 153 Hz to
1 25 MHz with CKI at 20 0 MHz
The contents of the SIO register may be accessed through
any of the memory access instructions Data waiting to be
transmitted in the SIO register is clocked out on the falling
edge of the SK clock Serial data on the SI pin is clocked in
on the rising edge of the SK clock
MICROWIRE PLUS Application
Figure 25 illustrates a MICROWIRE PLUS arrangement for
an automotive application The microcontroller-based sys-
tem could be used to interface to an instrument cluster and
various parts of the automobile The diagram shows two
HPC46064 microcontrollers interconnected to other MI-
CROWIRE peripherals HPC46064 1 is set up as the mas-
ter and initiates all data transfers HPC46064 2 is set up
as a slave answering to the master
The master microcontroller interfaces the operator with the
system and could also manage the instrument cluster in an
automotive application Information is visually presented to
the operator by means of an LCD display controlled by the
COP472 display driver The data to be displayed is sent
serially to the COP472 over the MICROWIRE PLUS link
Data such as accumulated mileage could be stored and re-
trieved from the EEPROM COP494 The slave HPC46064
could be used as a fuel injection processor and generate
timing signals required to operate the fuel valves The mas-
ter processor could be used to periodically send updated
values to the slave via the MICROWIRE PLUS link To
speed up the response chip select logic is implemented by
connecting an output from the master to the external inter-
rupt input on the slave
FIGURE 25 MICROWIRE PLUS Application
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