| abstract |
A structure and method for in-system programming of a programmable logic device are provided. The in-system programming structure provides one dedicated pin (mode) for in-system programming. Pins (SDI, SDO) are multiplexed with programmable input/output pins used in functional operations. When an enable signal is received at the dedicated pin, the multiplexed pins relinquish their roles as programmable input/output pin to become in-system programming pins. A state machine (400) controls the programming steps. The in-system programming structure can be cascaded in a 'daisy chain' fashion. |