LP5569 datasheet(28/93 Pages) TI2

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LP5569

SNVSAP8A – JULY 2017 – REVISED SEPTEMBER 2017

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(1)

This opcode is used with numerical operands.

(2)

This opcode is used with variables.

Table 7. Data Transfer and Arithmetic

INSTRUCTION

USAGE

COMPILER EXAMPLE

ld(1)

Assign a value to a variable.

ld ra, 33; load value 33h to local variable A

add(1)

Add the 8-bit value to the variable value.

add ra, 11; add value 11h to local variable A

add(2)

Add the value of variable 3 (global variable D) to the value of variable 2

(global variable C) and store the result in variable 1 (local variable A).

add ra, rc, rd; add the value in rd to rc and

store in ra

sub(1)

Subtract the 8-bit value from the variable value.

sub ra, 11; subtract value 11h from local

variable A

sub(2)

Subtract the value of variable 3 (global variable D) from the value of

variable 2 (global variable C) and store the result in variable 1 (local

variable A).

sub ra, rc, rd; subtract the value in rd from rc

and store in ra

(1)

This opcode is used with numerical operands.

(2)

This opcode is used with variables.

8.5.2.4 LED Driver Instructions

Table 8. LP5569 LED Driver Instructions

INST.

Bit

[15]

Bit

[14]

Bit

[13]

Bit

[12]

Bit

[11]

Bit

[10]

Bit

[9]

Bit

[8]

Bit

[7]

Bit

[6]

Bit

[5]

Bit

[4]

Bit

[3]

Bit

[2]

Bit

[1]

Bit

[0]

ramp(1)

pre-

scale

step time

sign

no. of increments

ramp(2)

pre-

scale

sign

step time

no. of

increments

set_pwm(1)

PWM value

set_pwm(2)

PWM value

wait

pre-

scale

time

8.5.2.4.1

Ramp

This is the instruction useful for smoothly changing from one PWM value into another PWM value on the LED0 to

LED8 outputs —in other words, generating ramps with a negative or positive slope. The LP5569 device allows

the programming of very fast and very slow ramps using only a single instruction. Full ramp 0 to 255 ramp time

ranges from 124 ms to 4 s.

The ramp instruction generates a PWM ramp, using the effective PWM value as a starting value. At each ramp

step the output is incremented or decremented by 1, unless the number of increments is 0. The time span for

one ramp step is defined with the prescale bit [14] and step-time bits [13:9]. The ramp instruction controls the

eight most-significant bits (MSB) of the PWM values and the remaining bits are interpolated as ramp mid-values

internally for smoother transition.

Prescale = 0 sets a 0.49-ms cycle time and prescale = 1 sets a 15.6-ms cycle time; so the minimum time span

for one step is 0.49 ms (prescale × step time span = 0.49 ms × 1) and the maximum time span is 15.6 ms × 31 =

484 ms/step. If all the step-time bits [13:9] are set to zero, the output value is incremented or decremented during

one prescale on the whole time cycle.

The number-of-increments value defines how many steps are taken during one ramp instruction: the increment

maximum value is 255, which corresponds to an increment from zero value to the maximum value. If PWM

reaches the minimum or maximum value (0 or 255) during the ramp instruction, the ramp instruction is executed

to the end regardless of saturation. This enables ramp instruction to be used as a combined ramp-and-wait

instruction. Note: the ramp instruction is a wait instruction when the increment bits [7:0] are set to zero.

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