AN2264 Motorola Semiconductor Products, AN2264 Datasheet - Page 2

• Manufacturer Part Number: AN2264
• Description: Freescale Semiconductor, Inc.
• Manufacturer: Motorola Semiconductor Products

AN2264/D
Hardware
2
The target MCU for the temperature display module is the MC68HC908EY16.
As this MCU was not available at the time of writing, this application note
employs an MC68HC908AZ60A. Implementation on an MC68HC908EY16
would significantly reduce the cost. Not only is the MC68HC908EY16 a lower
pin-count lower cost device but it will include an on-chip Internal Clock
Generator (ICG) obviating the need for a crystal or ceramic resonator.
The circuit diagram used in the temperature display application is shown in
figure 1. Apart from the MCU itself, two chips are required to facilitate a simple
LIN node. These are the LIN interface, in this case the MC33399 and a 5 volt
regulator. These chips will be replaced in the future by a single chip, the LIN
SBC. The regulator used is the 8-pin LT1121 which has the capability of
shutting down into a low power sleep mode under the control of the MCU. In
the arrangement shown it can be woken up via the MC33399 by LIN bus
activity.
The MC33399 includes the 30kohm LIN pull-up so this does not need to be
included on the PCB. The only discrete components required are pull-up
resistors for the IRQ and Reset pins, decoupling capacitors and a crystal and
its associated components. Two PortC pull-ups and a 9 volts zener circuit were
also included to facilitate entry into monitor mode using an external serial
interface. This facilitated in-circuit programming of the on-chip flash memory.
The software was developed on the prototype PCB fitted with a target header
for the MMDS development system rather than with an actual
MC68HC908AZ60A.
$CA
bit 0
bit 1
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
Freescale Semiconductor, Inc.
ID
For More Information On This Product,
Temperature sensor data encoded
in half Centigrade degree
increments from –30°C ($00) to
97.5°C ($FF).
LIN Node Temperature Display
Go to: www.freescale.com
Temperature Sensor
Table 1. Format of mirror response data
(byte 0)
LIN – bit error
LIN – checksum error
LIN – identifier parity error
LIN – slave not responding error
LIN – inconsistent sync. error
LIN – no bus activity error
not used
not used
Error status.
(byte 1)
MOTOROLA