PSI BOX Reference
IEEE Port
In both modes the DATA 0-7 lines and the DAV, NRFD
and NDAC lines are controlled according to the handshake in
progress.
The IEEE device address of the PSI BOX is front panel
DIP switchable in the range 0-15. A front panel LED flashes
whenever the IEEE port sends a byte, ie addressed to TALK. A
front panel LED flashes whenever the IEEE port receives a byte,
ie addressed to LISTEN.
As an IEEE device, in modes 1 and 2, the PSI BOX
responds to two addresses. The first address as set on the front
panel and is the IEEE to RS232 converter address. The second
address is one higher than this base address and is the IEEE to
Centronics Parallel converter address.
Each port may be addressed using secondary addresses.
These secondary addresses allow the IEEE controller to
interrogate the PSI BOX to determine the RS232 and Parallel
port configuration and indicate whether any data is in the input
and output buffers. They also allow the PSI BOX to perform
character conversion on the data passing through it.
As an IEEE controller the PSI BOX may accept data from
either the RS232 or the Centronics port and send it an IEEE
device on the IEEE port. The PSI BOX has a full controller
handshake.
The IEEE Leds.
______________
There are two LEDs dedicated to the IEEE port. LED 1
and 2 are used to indicate the flow of data through the IEEE
port.
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Chapter 3
