LP5523 datasheet(38/56 Pages) TI1

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LP5523

SNVS550D – SEPTEMBER 2009 – REVISED MAY 2013

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Table 6. LP5523 Branch Instructions(1) (continued)

wait for trigger

send a trigger

trigger

ext.

trig

Number of instructions to be skipped if

variable

jne

the operation returns true

Number of instructions to be skipped if

variable

the operation returns true

Number of instructions to be skipped if

variable

jge

the operation returns true

Number of instructions to be skipped if

variable

the operation returns true

Table 7. LP5523 Data Transfer and Arithmetic Instructions

Bit

Inst.

Bit [9] Bit [8] Bit [7] Bit [6] Bit [5] Bit [4] Bit [3] Bit [2] Bit [1] Bit [0]

[15]

[14]

[13]

[12]

[11]

[10]

target variable

8-bit value

add (i)

target variable

8-bit value

variable

add (ii)

target variable

sub (i)

target variable

8-bit value

variable

sub (ii)

target variable

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 LP5523 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 = 0.49ms x 1) and the maximum time span is 15.6 ms x 31 = 484ms/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.

Programming ramps with variables is very similar to programming ramps with numerical operands. The only

difference is that step time and number of increments are captured from variable registers, when the instruction

execution is started. If the variables are updated after starting the instruction execution, it will have no effect on

instruction execution. Again, at each ramp step the output is incremented/decremented by one unless increment

is 0. Time span for one step is defined with prescale and step time bits. Step time is defined with variable A, B, C

or D. Variables A, B and C are set with ld-instruction. Variable D is a global variable and can be set by writing the

VARIABLE register (address 3C). LED TEST ADC register (address 42) can be used as a source for the variable

D, as well. Note: Variable A is the only local variable which can be read throughout the serial bus. Of course, the

variable stored in 3CH can be read (and written), too.

Setting register 06H, 07H, or 08H bit LOG_EN high/low sets logarithmic (1) or linear ramp (0). By using the

logarithmic ramp setting the visual effect appears like a linear ramp, because the human eye behaves in a

logarithmic way.

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