lm8328tmx National Semiconductor Corporation, lm8328tmx Datasheet - Page 17

• Manufacturer Part Number: lm8328tmx
• Description: Mobile I/o Companion Supporting Keyscan, I/o Expansion Pwm, And Access.bus Host Interface
• Manufacturer: National Semiconductor Corporation

12.2.1 RAMP COMMAND
A RAMP command will vary the duty cycle of a PWM output
in either direction (up or down). The INCREMENT field spec-
ifies the amount of steps for the RAMP. The maximum amount
of steps which can be executed with one RAMP Command is
126 which is equivalent to 50%. The SIGN bit field determines
12.2.2 SET_PWM COMMAND
The SET_PWM command will set the starting duty cycle MIN
SCALE or FULL SCALE (0% or 100%). A RAMP command
12.2.3 GO_TO_START COMMAND
The GO_TO_START command jumps to the first command
in the script command file.
12.2.4 BRANCH COMMAND
The BRANCH command jumps to the specified command in
the script command file. The branch is executed with either
absolute or relative addressing. In addition, the command
15
15
0
15
15
0
1
INCREMENT
DUTYCYCLE
Bit or Field
PRESCALE
STEPTIME
Bit or Field
14
1
14
14
PRESCALE
0
SIGN
14
13
0
13
13
TABLE 11. Description of Bit and Building Fields of the SET_PWM Command
1
TABLE 9. Description of Bit and Building Fields of the RAMP Command
12
0
12
12
13
TABLE 12. GO_TO_START Command Bit and Building Fields
TABLE 10. SET_PWM Command Bit and Building Fields
TABLE 13. BRANCH Command Bit and Building Fields
11
0
12
TABLE 8. RAMP Command Bit and Building Fields
11
11
0 - 126
Value
1 - 63
Value
LOOPCOUNT
STEPTIME
255
0
1
0
1
11
0
10
0
10
10
10
9
0
Divide the 32.768 kHz clock by 16
Divide the 32.768 kHz clock by 512
Number of prescaled clock cycles per step
Increment ramp counter
Decrement ramp counter
Number of steps executed by this instruction; a value of 0 functions as a
WAIT determined by STEPTIME.
9
Duty cycle is 0%.
Duty cycle is 100%.
9
9
8
8
0
8
8
17
0
7
7
the direction of a RAMP (up or down). The STEPTIME field
and the PRESCALE bit determine the duration of one step.
Based on a 32.768 kHz clock, the minimum time resulting
from these options would be 0.49 milliseconds and the max-
imum time for one step would be 1 second.
following the SET_PWM command will finally establish the
desired duty cycle on the PWM output.
gives the option of looping for a specified number of repeti-
tions.
Please note: Nested loops are not allowed.
SIGN
7
7
ADDR
6
6
6
6
5
Description
Description
5
5
5
DUTYCYCLE
4
4
4
4
STEPNUMBER
INCREMENT
3
3
3
3
2
2
2
2
1
1
1
1
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