vsc055xkm-01 Maxim Integrated Products, Inc., vsc055xkm-01 Datasheet - Page 83

• Manufacturer Part Number: vsc055xkm-01
• Description: Enhanced I?c Backplane Controller
• Manufacturer: Maxim Integrated Products, Inc.

VSC055-01
Data Sheet
3.2.76 8Ch: Pulse Train Control 90 (PTC90)
This register, along with the PTC91 register, provides a user-programmable LED flashing pulse train that
defines the 0.25 Hz flash rate (selectable in the bit control registers) at power on. The user can adjust the
pulse duration, pulse train length, and the on/off time to derive a specific visual indication. The PTC90
register provides eight of the twelve bits available in the programmable pulse train. The PTC91 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
PTC90 register with a 45h and the PTC91 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 PTC91 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
V
value in bits 3:0 of the Clock Select Control register. For information on the Clock Select Control register,
see
The following table shows the bit assignments for the Pulse Train Control 90 registers.
Register Name:
Address:
Reset Value:
Description
Bit
7:0
DD
“FDh: Clock Select Control (CSC),”
, connect an external 10 kΩ pull-up resistor to the SYNC# pin, and place the proper synchronization
Bit Label
PT7-0
PTC90
8Ch
0011_1111b
Pulse Train Control 90
Access
R/W
Description
Pulse Train
These eight bits are the first bits shifted out from 0 to 7 and define the on/off
time for the 0.25 Hz (FS2-FS0 = 001b in the selected bit control register) flash
rate.
1: defines LED on time.
0: defines LED off time.
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January 2008
Revision 4.1