When I try to fit a CoolRunner XPLA3 device, the following error occurs:
"ERROR:Cpld:1060 - Design contains X unique output enables, exceeds device limit 9."
How do I know the limit of output enables (OE) for the device?
For CoolRunner XPLA3, see the "CoolRunner XPLA3 CPLD Family" data sheet, Figure 6: "I/O Cell" located at:
Each function block has four Control Terms (CT 3:0) plus one Universal OE. Universal OE is global, so there is one per device. Then you can count the number of output enables available as follows:
1 Universal OE + (# FB x 4) = Total Output Enable limit
This yields the total number of output enables. Note that control terms are shared with other functions, so using a control term clock, control term asynchronous reset or preset, or clock enable reduces the number of output enables that may be used in your design.