28824 Parallax Inc, 28824 Datasheet - Page 4

• Manufacturer Part Number: 28824
• Description: SERVOPAL SERVO PULSER TIMER
• Manufacturer: Parallax Inc

Specifications of 28824

• Accessory Type: Servo Motor Control
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: BASIC Stamp®
• For Use With: 28803 - KIT BOARD OF EDU W/O PWR SUPP
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

To terminate a sequence of pulses on /Inp, just wait at least 2mS before sending another pulse. This
signals the ServoPAL that the next pulse is intended for Servo 0.
Now, what if you want to program only Servo 1 and leave Servo 0 alone? That’s easy, as well. Just
send a very short pulse (4 – 100µS) for Servo 0 first, then a pulse for Servo 1. The ServoPAL will
interpret the short pulse as indicating that you don’t want to change Servo 0’s pulse stream, if one has
already been programmed. Here’s an example:
PULSOUT nInp, 2
PULSOUT nInp, 500
Here’s what the resulting waveforms look like:
And finally, what if you want to terminate a servo’s pulse stream? The ServoPAL will only send pulses to a
servo that are between approximately 0.5 and 2.5mS. If it encounters a request for pulses well outside
this range, it will cease sending pulses to the affected servo. Here’s how you can use this to stop sending
pulses to a servo:
PULSOUT nInp, 2000
Here’s the result:
To summarize, here’s a table showing the various pulse durations and what they mean:
© Parallax, Inc. • ServoPAL (2007.10.30)
Servo 0
Servo 1
Servo 0
Servo 1
Servo 0
Servo 1
Note: Do not send the ServoPAL any pulses less than 4µS in duration. It could easily become
confused, as it might miss them entirely.
/Inp
/Inp
/Inp
4 - 100µS
0.5 - 2.5mS
'Send a 4mS pulse to Servo 0.
Skip this servo. (Don’t change its output.)
Program this pulse width into the affected servo.
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