vsc055xkm-01 Maxim Integrated Products, Inc., vsc055xkm-01 Datasheet - Page 84

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

3.2.77 8Dh: Pulse Train Control 91 (PTC91)
Revision 4.1
January 2008
This register, along with the PTC90 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, the 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 PTC90 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 91 registers.
Register Name:
Address:
Reset Value:
Bit
7:6
5:4
3:0
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
TPW1-0
PTL1-0
PT11-8
PTC91
8Bh
1000_0000b
Access
R/W
R/W
R/W
Description
Train Pulse Width
These two bits define the pulse width of each of the pulse train bits. The
available pulse widths are as follows:
Pulse Train Length
These two bits define the pulse train length, which is the number of pulse train
bits that is shifted out before returning to bit 0. The available pulse train lengths
are given below.
Pulse Train
These four bits are the last bits shifted out from 0 to 3 and define the on/off time
for the flash rate.
1: defines an LED on time.
0: defines an LED off time.
TPW1
page 111.
PTL1
0
0
1
1
0
0
1
1
84 of 133
TPW0
PTL0
0
1
0
1
0
1
0
1
Train Pulse Width
166.67 ms
250.0 ms
333.3 ms
500.0 ms
Pulse Train Length
12 pulse train bits from 0 to 11
10 pulse train bits from 0 to 9
9 pulse train bits from 0 to 8
8 pulse train bits from 0 to 7
VSC055-01
Data Sheet