MC68HC55 Datasheet, PDF (4/40 Pages) Freescale Semiconductor, Inc – Two-Channel CMOS ASIC Device

MC68HC55 Technical Data
CSU - CENTRAL SENSING UNIT
MC68HC16P3
MCU
PWM Pin
MC68HC55
SCLK
DSI0F
DSI0S
DSI0R
SCK
MOSI
MISO
I/O Pin
CLK
DSI1F
DI
DSI1S
DO
DSI1R
CS
DSI/P
DSI0O
GND
DSI1O
GND
2-WIRE BUS
SIGNAL
RETURN
•••
SLAVE 1
SLAVE 2
SLAVE 3
SLAVE 4
Figure 1-1. DSI System Connections
(Other Arrangements Possible)
SLAVE 15
After reset, the master MCU must first configure the DSI system by
assigning a unique 4-bit address to each remote peripheral unit on the
2-wire DSI bus. When the system is initially powered up, the 2-wire bus
idles at about 25 volts to provide power to the local power supply
capacitor at the first node of the distributed bus. A bus switch in each
peripheral node is initially opened until that node has been programmed
with a 4-bit address. After power up, the 2-wire bus only goes as far as
the first node. The master MCU provides a series of SPI commands to
the DSI/D to send a 16-bit (plus 4-bit CRC) message instructing it to
assign a 4-bit address to the first node. Address 0000 is a global address
which addresses all nodes whether or not they have been initialized with
their unique 4-bit address. During this first message, no remote node will
respond (provide return data to the master). This first message sets the
address of the first node, which causes it to close its bus switch.The bus
now goes to the first and second nodes along the 2-wire bus, and the
second node power supply capacitor becomes charged by the 25-volt
idle level on the bus.
Technical Data
4
MC68HC55
DSI/D (Distributed System Interface – Digital)