ADLINK Technology PCI-8254, User Manual

Page: 186 / 226

172 Motion Control Theory
b. Mode 2: PWM frequency mode with fixed width
This control mode changes PWM frequency according to speed at
fixed PWM pulse width. Under fixed PWM pulse width W, the VAO
table gives PWM frequency 1/T
1
, 1/T
2
and 1/T
3
at speed V
1
, V
2
and V
3
as shown in figure below. To use this mode to
1. Set up control mode: Use APS_set_vao_param( ) to set
up
value of VAO_TABLE_OUTPUT_TYPE
parameter to 0x2
.
2. Set up fixed PWM output pulse width:
Use APS_set_vao_param( ) to set up parameter
VAO_TABLE_PWM_Config in unit of ns. Valid input
range is 20ns ~ 335544320 ns
。