MC33192 Datasheet, PDF (4/12 Pages) Motorola, Inc – MI-Bus Interface Stepper Motor Controller

Freescale SMeCm33i1c9o2nductor, Inc.
MI–Bus Access Method
The information on the MI–Bus is sent in a fixed message
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 (3ts) held constantly at a Logic
“0” state.
Push–Pull Communication Sequence
Communication between the system MCU and slave
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.
Figure 2. Push Field Data Bits
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{Bit Name}
Control Function
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{D4 Inh2 Inhibits H–Bridge 2}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{D3 Dir2 Establishes Direction of H–Bridge 2 Current}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{D2 E}
Energizes Bridge Coils 1 and 2
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{D1 Dir1 Establishes Direction of H–Bridge 1 Current}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{D0 Inh1 InhibitsH–Bridge1}
After the Pull Sync bit is sent, following the Push Field, the
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 address selected MC33192 device sends data, in
the form of status bits, back to the MCU reporting the
devices condition. At the end of the Push Field the MCU
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.
Figure 3. Pull Field Status Bits
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{S2 S1 S0}
Status
Comments
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{0 0 0 Notused}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{0 0 1 Free}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{0 1 0 No Back EMF Drivers and/or coils failed}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{0 1 1 Free}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{1 0 0 Normal/OK}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{1 0 1 Thermal}
Chip temperature > 150°C
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{1 1 0 Programming PROM energized}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ _{1 1 1 Selection failed Noise on MI–Bus, failed or}
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ ^{disconnected module}
The positive edge of the Pull Sync pulse (set by the MCU)
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
The communication between the MCU and the selected
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
An error is detected when the Pull Field contains the code
“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.
Figure 4. MI–Bus Timing Diagram
Frame
Push Field
Pull Field
Push Sync
Data
Address
Data End–of–Frame
MI–Bus Wire
3ts
3ts
1 23 45 67 89
1 2 34
Start “1” “0” D0 D1
75 µs
D2 D3 D4 A0 A1 A2 “0” “1” S2 S1 S0
NRZ
Bi–Phase Coded
Pull Sync
Coded
475 µs
100 µs
Start
Oscillator
Frequency
÷ 32 = 20 kHz
Push/Pull Function
Strobe
4
Push
Pull
Strobe Pulse
MOTOROLA ANALOG IC DEVICE DATA
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