National Instruments DIO 6533 사용자 설명서
Chapter 5
Signal Timing
© National Instruments Corporation
5-19
DIO 6533 User Manual
Long-Pulse Mode
Long-pulse mode is a variant of leading-edge mode. The only
difference is the effect of a data-settling delay, if used. In long-pulse
mode, a programmable delay, rather than delaying the ACK pulse,
increases the minimum width of the pulse.
difference is the effect of a data-settling delay, if used. In long-pulse
mode, a programmable delay, rather than delaying the ACK pulse,
increases the minimum width of the pulse.
Long-pulse mode enables you to handshake with a peripheral device
that requires a large minimum pulse width.
that requires a large minimum pulse width.
Long-pulse mode also enables you to handshake with 8255 emulation
mode, if you set the ACK and REQ signals to active low. If you want to
use long-pulse mode to handshake with an actual 8255 or 82C55 PPI,
make sure you select an adequate minimum pulse width for your 8255
or 82C55. A data-settling delay of 500 ns is sufficient for any current
8255 or 82C55 PPI.
mode, if you set the ACK and REQ signals to active low. If you want to
use long-pulse mode to handshake with an actual 8255 or 82C55 PPI,
make sure you select an adequate minimum pulse width for your 8255
or 82C55. A data-settling delay of 500 ns is sufficient for any current
8255 or 82C55 PPI.
and output diagrams, respectively.
Figure 5-16. Long-Pulse Mode Input
Wait
For
Space
Wait
For
REQ
Programmable
Delay
Programmable
Delay
Wait
For
REQ
When REQ
Asserted
When 6533 Device
Has Space For Data,
Input Data*
Clear
ACK
Pulse
When REQ
Unasserted
Unasserted
Initial State
ACK Cleared
Send
ACK Pulse
* With REQ-edge latching enabled, the data read
is from the last active-going REQ edge.