LM8323 datasheet(21/46 Pages) TI2

21 / 46 page

LM8323

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SNLS273A – JULY 2010 – REVISED MARCH 2013

NOTE

The PWM_STOP command might not take immediate effect if the current command being

executed is a command with long execution time. If a PWM_STOP command is sent when

the PWM engine is running a long RAMP command, the PWM will only stop after the

RAMP is completed.

The script commands have their own fixed-length 16-bit format and encoding unrelated to the variable-length,

byte-based format used for host commands. A script command is sent by the host to the LM8323 as a parameter

to the PWM_WRITE command. Another parameter to the PWM_WRITE command specifies an address in the

script command file for receiving the command.

COMMAND QUEUE

After the host issues a PWM_START command, script commands are read from the script command file into a

command queue which consists of a command file output register, command buffer, and active command

allows seamless back-to-back command execution.

A command loaded into the command file output register is synchronized to the 32.768 kHz clock and stored in

the command buffer. If no command is currently active, the command passes through to the active command

command buffer. On completion of the currently active command, the contents of the command buffer are

transferred to the active command register, and the command buffer may then receive a new command.

The host does not have direct access to any of the registers in the command queue. The operations which read

script commands from the script command file occur automatically after the host issues the PWM_START

command.

Script execution stops when the host sends a PWM_STOP command or when the script engine executes an

END command. Executing an END command asserts IRQ to the host.

PWM TIMER OPERATION

The timers implement a fixed 256-cycle period with a programmable duty cycle and programmable ramp-

up/ramp-down of the duty cycle. Figure 15 shows the architecture of a PWM timer.

Figure 15. PWM Timer

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LM8323 Datasheet(PDF) 21 Page - Texas Instruments