FLEX 10K Embedded Programmable Logic Device Family Data Sheet
I/O Element
An I/O element (IOE) contains a bidirectional I/O buffer and a register
that can be used either as an input register for external data that requires
a fast setup time, or as an output register for data that requires fast clock-
to-output performance. In some cases, using an LE register for an input
register will result in a faster setup time than using an IOE register. IOEs
can be used as input, output, or bidirectional pins. For bidirectional
registered I/O implementation, the output register should be in the IOE
and, the data input and output enable register should be LE registers
placed adjacent to the bidirectional pin. The Compiler uses the
programmable inversion option to invert signals from the row and
column interconnect automatically where appropriate. Figure 13 shows
the bidirectional I/O registers.
Altera Corporation
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