33970 Datasheet, PDF (22/36 Pages) Freescale Semiconductor, Inc – Dual Gauge Driver Integrated Circuit with Improved Damping Algorithms

FUNCTIONAL DEVICE OPERATION
LOGIC COMMANDS AND REGISTERS
The bits in Table 18 are read-only bits.
ENB1 (OD15) — This bit indicates if Gauge 1 is enabled.
• 0 = Disabled
• 1 = Enabled
DIR1 (OD14) — This bit indicates the direction Gauge 1
pointer is moving.
• 0 = Toward position 0
• 1 = Away from position 0
DIRC1 (OD13) — This bit determines if the direction of the
most recent pointer movement is toward, or away from, the
last commanded position.
• 0 = Direction of the pointer movement is toward the
commanded position
• 1 = Direction of the pointer movement is away from the
commanded position
CMD1 (OD12) — This bit indicates if Gauge 1 is at the most
recently commanded position.
• 0 = At commanded position
• 1 = Not at commanded position
POS11:POS0 (OD11:OD0) — These 12 bits represent the
actual position of the pointer at the time CS transitions to a
logic [0].
Gauge 0 and 1 Pointer Velocity Status Information
Most recent valid PECCR command resulting in the
Gauge 0 and 1 Pointer Velocity status output:
D11
D10
D9
D8
1
1
1
x
x = Don’t care.
Table 19. Gauge 0 and 1 Pointer Velocity Status Output Register
Bits OD15 OD14 OD13 OD12 OD11 OD10 OD9 OD8 OD7 OD6 OD5 OD4 OD3 OD2 OD1 OD0
Read 1V7 1V6 1V5 1V4 1V3 1V2 1V1 1V0 0V7 0V6 0V5 0V4 0V3 0V2 0V1 0V0
Write –
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
The bits in Table 19 are read-only bits.
1V7:1V0 (OD15:OD8) — These eight bits represent the
velocity position value (refer to Table 21, page 24) indicating
the actual velocity of Gauge 1 pointer at the time CS
transitions to a logic [0].
0V7:0V0 (OD7:OD0) — These eight bits represent the
velocity position value (refer to Table 21) indicating the
actual velocity of Gauge 0 pointer at the time CS transitions
to a logic [0].
STATE MACHINE OPERATION
The two-phase step motor has maximum allowable
velocities and acceleration and deceleration.The purpose of
the step motor state machine is to drive the motor with
maximum performance while remaining within the motor’s
voltage, velocity, and acceleration constraints.
A requirement of the state machine is to ensure the
deceleration phase begins at the correct time and pointer
position. When commanded, the motor will accelerate
constantly to the maximum velocity, then move toward the
commanded position. Eventually, the pointer will reach the
calculated location where the movement has to decelerate,
slowing safely to a stop at the desired position. During the
deceleration phase, the motor will not exceed the maximum
deceleration.
During normal operation, both step motor rotors are
microstepped with 24 steps per electrical revolution (see
Figure 9). A complete electrical revolution results in two
degrees of pointer movement. There is a second (smaller)
state machine in the IC controlling these microsteps. This
state machine receives clockwise or counter-clockwise index
commands at intervals, stepping the motor in the appropriate
direction by adjusting the current in each coil. Normalized
values are provided in Table 20, page 23.
33970
22
Analog Integrated Circuit Device Data
Freescale Semiconductor