Why is there a difference in the SDR instruction line?
For 9500XL devices there is a difference between the SVF file and the JTAG Programmer output. The JTAG Programmer sets minimum values to internal timers in the XC9500XL CPLDs. These internal timers are set to a maximum value when the command is issued through the SVF file. This is because some test equipment will require the maximum value in the SVF file. Both versions of the command will complete the isp enable instruction.
This difference between the SVF file and the JTAG Programmer does not apply to the XC9500 devices (only to the XC9500XL devices).