L298 more speed needed (4 replies)

Hi Everyone

I've got a Solarbotics L298 stepper motor driver, various stepper motors nema11, 23, 17, 34, and a Comfiletech Cubloc cb290 PLC embedded controller.
I've read somewhere that the stepper motor is able to rotate at high speed but it's losing torque.
So I need to run a stepper motor around 200 rpm.
The PLC code is written in basic language. The code:

Const Device = CB290
Set Outonly On
Usepin 16, Out, l1
Usepin 17, Out, l2
Usepin 18, Out, l3
Usepin 19, Out, l4
Usepin 14, Out, en1
Usepin 15, Out, en2
Dim a As Byte
Dim b As Byte
Dim c As Integer
Do
c=In(72)

If c=1 Then
High 14
High 15
For a=1 To 200
Byteout 2, 1
Delay 5
Byteout 2, 4
Delay 5
Byteout 2, 2
Delay 5
Byteout 2, 8
Next

End If


The ports 16 to 19 are on the port2, so I can give impulses with byteout like

1000 0000 '(16)
delay x
0100 0000 '(17)
delay x
0010 0000 '(18)
delay x
0001 0000 '(19)
delay x

I've tried with various delays, but the motor won't rotate faster than 60 rpm.
Can anyone help me?

p.s. Sorry for my bad english