MD1

Mode 1, Output Pad Used for Readback Data Output

The MD1 output pad is connected to the Mode 1 (M1) output pin, which is used to determine the configuration mode on XC4000 and XC5200 devices. Following configuration, MD1 can be used as a 3-state or simple output pad, but it must be connected through an OBUF or an OBUFT to the user circuit. However, the user output signal must not interfere with the device configuration. XC5200 devices allow an MD1 pad to be used as an input pad; XC4000 devices do not. The IOB associated with an MD1 pad has no flip-flop or latch. This pad is usually connected to the DATA output of the READBACK function, and the output-enable input of the 3-state OBUFT is connected to the RIP output of the READBACK function.