LP55231 datasheet(39/53 Pages) TI

39 / 53 page

LP55231

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SNOSCR5 – MARCH 2013

Table 6. LP55231 Branch Instructions (continued)

Bit

Inst.

Bit [8]

Bit [6]

Bit [5]

Bit [3] Bit [2]

Bit [1] Bit [0]

[15]

[14]

[13]

[12]

[11]

[10]

[9]

[7]

[4]

wait for trigger

send a trigger

trigger

ext.

X(3)

trig

Number of instructions to be skipped

variable

jne

if the operation returns true

Number of instructions to be skipped

variable

if the operation returns true

Number of instructions to be skipped

variable

jge

if the operation returns true

Number of instructions to be skipped

variable

if the operation returns true

(3)

X means do not care.

Table 7. LP55231 Data Transfer and Arithmetic Instructions

Bit

Inst.

Bit [8]

Bit [6]

Bit [5]

Bit [3] Bit [2]

Bit [1] Bit [0]

[15]

[14]

[13]

[12]

[11]

[10]

[9]

[7]

[4]

target

8-bit value

variable

target

add(1)

8-bit value

variable

variabl variabl

target

add(2)

variable

target

sub(1)

8-bit value

variable

variabl variabl

target

sub(2)

variable

(1)

This opcode is used with numerical operands.

(2)

This opcode is used with variables.

LED Driver Instructions

RAMP

This is the instruction useful for smoothly changing from one PWM value into another PWM value on the D1 to

D9 outputs; in other words, generating ramps (with a negative or positive slope). The LP55231 allows

programming very fast and very slow ramps.

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

the output is incremented/decremented by one unit, unless the number of increments is 0. Time span for one

ramp step is defined with prescale -bit [14] and step time -bits [13:9]. Prescale = 0 sets 0.49 ms cycle time and

prescale = 1 sets 15.6 ms cycle time; so the minimum time span for one step is 0.49 ms (prescale * step time

span = 0.49 ms x 1) and the maximum time span is 15.6 ms x 31 = 484 ms/step.

Number of increments value defines how many steps will be taken during one ramp instruction; increment

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

minimum/maximum value (0/255) during the ramp instruction, ramp instruction will be executed to the end

regardless of saturation. This enables ramp instruction to be used as a combined ramp & wait instruction. Note:

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

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