mc33192dw Freescale Semiconductor, Inc, mc33192dw Datasheet - Page 4

• Manufacturer Part Number: mc33192dw
• Description: Mi-bus Interface Stepper Motor Controller
• Manufacturer: Freescale Semiconductor, Inc

MI–Bus Access Method
frame format (See Figure 4). The system MCU can take
control of the MI–Bus at any time with a start bit which
violates the law of Manchester Bi–Phase code by having
three consecutive Time Slots (3t s ) held constantly at a Logic
“0” state.
Push–Pull Communication Sequence
MC33192 devices always use the same message frame
organization. The MCU first sends eight serial data bits over
the MI–Bus comprised of five control bits followed by three
address bits. This communication sequence is called a “Push
Field” since it represents command information sent from the
MCU. The sequence of the five control data bits follow the
order D0, D1, D2, D3 and D4. The three address bits are sent
in sequential order A0, A1 and A2 defining a binary address
code. The condition of MI–Bus during any of the control bit
time windows defines a specific control function as shown in
Figure 2. A “Pull Sync” bit is sent at the end of the Push Field,
the positive edge of which causes all data sent to the
selected device to be latched into the output circuit.
MCU listens on the MI–Bus for serial data bits sent back from
the previously addressed MC33192 device. This portion of
the communication sequence starts the “Pull Field Data”
since it represents information pulled from the addressed
MC33192 and received by the MCU.
the form of status bits, back to the MCU reporting the
devices condition. At the end of the Push Field the MCU
Push/Pull Function
Bit
D4
D3
D2
D1
D0
4
The information on the MI–Bus is sent in a fixed message
Communication between the system MCU and slave
After the Pull Sync bit is sent, following the Push Field, the
The address selected MC33192 device sends data, in
MI–Bus Wire
Name
Inh2
Dir2
E
Dir1
Inh1
Strobe
Figure 2. Push Field Data Bits
Inhibits H–Bridge 2
Establishes Direction of H–Bridge 2 Current
Energizes Bridge Coils 1 and 2
Establishes Direction of H–Bridge 1 Current
Inhibits H–Bridge 1
75 s
Start
3t s
Push Sync
“1” “0” D0
1
Control Function
2
D1
3
Data
D2
Figure 4. MI–Bus Timing Diagram
Push Field
4
Bi–Phase Coded
D3
475 s
5
Push
Frame
MC33192
D4
6
A0
7
Address
outputs a Pull Sync bit which signals the start of the Pull
Field. In the Pull Field are three bits (S2, S1 and S0) which
report the status of the previously addressed MC33192
according to Figure 3.
causes all Push Field Data sent to the selected MC33192 to
be stored in the output latch circuit in time with the strobe
pulse. This means the data bits are emitted in real time
synchronization with the MCU’s machine cycle. The strobe
pulse occurs only after the Push Field sequence is validated
by the address selected device.
Message Validation
MC33192 device is valid only when the MCU reads
(receives) the Pull Field Data having the correct codes
(excluding the code “1–1–1” and “0–0–0”) followed by an
End–of–Frame signal. The frequency of the End–of–Frame
signal may be a sub–multiple of the selected devices local
oscillator or related to an internal or external analog
parameter using a Voltage to Frequency Converter.
Error Detection
“1–1–1” followed by the End–of–Frame permanently tied to a
logic “1” state (internally from 5.0 V through a pull–up
resistor). This means the communication between the MCU
and the selected device was not obtained.
Pull Sync
S2
A1
0
0
0
0
1
1
1
1
8
The positive edge of the Pull Sync pulse (set by the MCU)
The communication between the MCU and the selected
An error is detected when the Pull Field contains the code
S1
A2
0
0
1
1
0
0
1
1
9
S0
0
1
0
1
0
1
0
1
“0”
Figure 3. Pull Field Status Bits
“1”
1
Strobe Pulse
Not used
Free
No Back EMF
Free
Normal/OK
Thermal
Programming
Selection failed
100 s
MOTOROLA ANALOG IC DEVICE DATA
S2
2
Coded
Data
NRZ
Status
S1
3
S0
Pull Field
4
End–of–Frame
Pull
Drivers and/or coils failed
Chip temperature > 150 C
PROM energized
Noise on MI–Bus, failed or
disconnected module
Frequency
32 = 20 kHz
Oscillator
Comments
3t s
Start