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CHAPTER 5: Peripheral Operation
DIO7 rsv
serial-poll status information
This bit is defined by the IEEE 488 Specification and is used
to indicate to the bus controller that the interface converter is
the bus device that requested service. It is cleared when the
interface is serial polled by the controller.
DIO6 Not Defined—Always “0”
DIO5 Serial Input Buffer NOT EMPTY
This bit is set when the serial input buffer contains one or
more data bytes which have not been sent out the IEEE bus.
It is cleared, set to “0,” when the buffer is empty.
DIO4 IEEE Input Buffer Full
When this bit is set, it indicates that the interface converter
may hold off the controller on subsequent data transfers. The
interface may continue to accept an additional 512 characters,
depending on the size of the serial input buffer.
DIO3 Received Last Serial Terminator
If the Peripheral SRQ feature is enabled, the interface
converter will issue a request for service by asserting the SRQ
line and setting this bit along with the rsv bit (DIO7). It is
cleared, along with rsv, when serial polled by the controller.
If this feature is not enabled, this bit is always “0.”
DIO2 Serial Handshake
This bit indicates the present state of the serial handshake.
If it is set to “1,” the serial device connected to the interface
converter is capable of accepting serial data. If “0,” the RTS
line is unasserted, if configured for hardware handshake, or
the “X-OFF” character has been received, if configured for
X-ON/X-OFF software handshake.
DIO1 Not Used—Always “0”