MC33192 Datasheet, PDF (9/12 Pages) Motorola, Inc – MI-Bus Interface Stepper Motor Controller

Freescale SMeCm33i1c9o2nductor, Inc.
programming OK code “100” indicating the address
programming to be executed.
The First and Second Instructions must be repeated until
the MCU successfully receives the programming code
“100”. Address programming is not complete until a “100”
OK status is received by the MCU with the MI–Bus voltage
at 5.0 V.
Overwrite–Bit Programming involves the use of two
instructions. See Figure 11.
First Instruction Have the MI–Bus continuously set at
12 V so as to have the MC33192 in the programming mode.
Programming can only be accomplished with the MI–Bus at
12 V.
The MCU serially enters “Logic Zeros” for the Push Field
Data bits D0, D1, D2 and D3 and a Logic “1” for D4 bit
followed by the programmed address bits A0, A1 and A2.
The MCU now waits 275 µs before starting the second
instruction. The total of the Pull time, Delay time, and Bus
Violation time (V) of the second instruction (150 µs, 275 µs
and 75 µs respectively) will cause the memory cell to be
energized for 500 µs. During the first 150 µs of this time, the
MCU is checking the Pull Field Data Bits for the status of bits
S2, S1 and S0 looking for the programming code “110” to
indicate complete activation of the memory cell.
Second Instruction (MI–Bus remaining at 12 V)
The MCU repeats the first instruction outlined above until
the programming OK code “100” is sent back to the MCU
from the selected MC33192 indicating the overwrite–bit
protection to be programmed. If after eight repeat
instructions, the programming code “110” or the OK code
“100” is not generated four times in succession,
programming of the MC33192 has failed. If this occurs, the
Overwrite–Bit Programming sequence should be reviewed
and re–started from the beginning.
H–Bridge Output
The H–Bridge output drive circuit and associated
diagnostic encoder are shown in Figure 12. The H–Bridge
output uses internal diode clamps (D1, D2, D3, D4) to provide
transient protection of the output transistors necessary when
switching inductive loads associated with stepper motors.
Back EMF Detection
Three different Back EMF currents can occur depending
on whether the motor is running or manner in which it is being
stopped. Referring to Figure 12; When the Dir1 bit is set to
logic 0, the direction of current flow will be from VCC through
transistor Q2, Coil A (A1 to A2), and transistor Q4 to ground.
1) Fast Decay (when transistors Q1, Q2, Q3 and Q4 are
switched off).
When the current flowing in the coil is stopped by setting
the Inh1 bit to logic 0, the back EMF current will circulate
through the voltage supply (VCC) and diodes D1 and D3. At
that time, the voltage developed across the diode D1 is
detected by transistor Q6. The generated voltage pulse of Q6
is then encoded and sent, in the Pull–Field, to the
microprocessor.
2) Slow Decay (Q3 and Q4 are switched off)
When the current flowing in the coil is stopped by setting
the E bit to logic 0, the back EMF current will circulate through
the diode D1 and transistor Q2 which is already switched on.
3) When Motor is Running
The rotational direction of the motor changes whenever
the Dir bit state is changed. When the Dir bit is changed from
a logic 0 to a logic 1, transistors Q2 and Q4 are switched off
and transistors Q1 and Q3 are switched on. At this time, the
back EMF current will circulate from ground through diodes
D1 and D3 to the voltage supply (VCC). In all cases, the back
EMF currents will be detected by transistors Q5 and Q6.
Active
Programming
Finished
12V
MI–Bus Voltage
5.0 V
Instruction Number
V
MI–Bus Field
Address
Status Code
Overwrite–Bit
Status Code
Strobe Pulse
Energy in
Memory Cell
Figure 11. Address Programming Diagram
1
Push
550 µs
Pull Delay V
150 µs 275 µs 75 µs
“110”
12 V
5.0 V
2
Push
550 µs
Pull Delay V
150 µs 275 µs 75 µs
“110”
Finished
3
Push
Pull
“100”
“110”
“100”
“100”
OK
500 µs
475 µs
500 µs
t
MOTOROLA ANALOG IC DEVICE_FD_oA_rT_MA _{ore Information On This Product,}
9
Go to: www.freescale.com