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VSC056

Data Sheet

Revision 4.1

January 2008

3.2.65 78h: Pulse Train Control 40 (PTC40)

This register, along with the PTC41 register, provides a user-programmable LED flashing pulse train. The

user can adjust the pulse duration, the pulse train length and the on/off time to derive a specific visual

indication. The PTC40 register provides eight of the twelve bits available in the programmable pulse train.

The PTC41 register contains two bits of pulse-width programmability, two bits of pulse train length

programmability, and the remaining four bits of the programmable pulse train.

As an example, the pulse train can be used to develop a visual heartbeat indication by programming the

PTC40 register with a 45h and the PTC41 register with a 01h. This combination develops a pulse train

with two blinks followed by a gap with the on times of the LED equal to 166.67 ms.

If the default values of this register or the PTC41 register are modified, and synchronization to other LED

flash rates is desired, the SYNC# pin must be enabled. To enable the SYNC# pin, tie the SYNCEN pin to

VDD, connect an external 10 kΩ pull-up resistor to the SYNC# pin, and place the proper synchronization

value in bits 3:0 of the Clock Select Control register. For information on the Clock Select Control register,

see “FDh: Clock Select Control (CSC),” page 111.

The following table shows the bit assignments for the Pulse Train Control 40 register.

PTC40

Address:

78h

Reset Value:

0000_0000b

Bit

Bit Label

Access

Description

7:0

PT7-0

R/W

Pulse Train

These eight bits are the first bits shifted out from 0 to 7 and define the on/off

time for the flash rate.

1: defines LED on time.

0: defines LED off time.

VSC056 Datasheet(PDF) 70 Page - Maxim Integrated Products