Chapter 5 Signal Timing
© National Instruments Corporation 5-23 DIO 6533 User Manual
Trailing-Edge Mode
In trailing-edge mode, the 6533 device and the peripheral device send
each other pulses on the ACK and REQ lines. The trailing edge of the
ACK or REQ pulse indicates that the 6533 device or peripheral device
is ready for a transfer.
Input
In input mode, the 6533 device sends an ACK pulse of programmable
width when ready to receive data. After receiving the trailing edge of
the ACK pulse, the peripheral device can strobe data into the 6533
device by deasserting the REQ signal. The 6533 device sends another
ACK pulse when ready for another input.
To slow down the handshake, you can specify a data-settling delay to
increase the ACK pulse width.
Output
In output mode, the 6533 device sends an ACK pulse of programmable
width after driving output data to indicate new, valid output data. The
peripheral device can latch the data on the falling or rising edge of the
ACK signal, or at any time before ending the REQ pulse. The peripheral
device must respond with a REQ pulse, the trailing edge of which
deasserts the ACK signal and requests additional data.
To slow down the handshake, you can specify a data-settling delay to
increase the ACK pulse width and, therefore, the setup time from valid
output data to the trailing edge of the ACK signal.