ADLINK Technology PCI-3488, Руководство пользователя

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Operation Theory 27
Data Lines
DIO1 to DIO8 carry both data and command messages. All com-
mands and most data use the 7-bit ASCII code, the 8th bit, DIO8,
is either unused or for parity check.
Handshake Lines
These three handshake lines control the transfer of data/mes-
sages between devices.
X
DAV (Data Valid): used to indicate the condition (availability
and validity) of information on the DIO signal lines
X
NRFD (Not Ready For Data): used to indicate the condition
of readiness of device(s) to accept data
X
NDAC (Not Data Accepted): used to indicate the condition
of acceptance of data by device
System management lines
These five system management lines manage the flow of control
and data bytes across the interface.
X
EOI (End or Identify): used (by a talker) to indicate the end
of a multiple byte transfer sequence or, in conjunction with
ATN (by a controller), to execute a polling sequence
X
IFC (Interface Clear): used (by a controller) to place the
interface system, portions of which are contained in all inter-
connected devices, in a known quiescent state
X
SRQ (Service Request): used by a device to indicate the
need for attention and to request an interruption of the cur-
rent sequence of events
X
ATN (Attention): used (by a controller) to specify how data
on the DIO signal lines are to be interpreted and which
devices must respond to the data
X
REN (Remote Enable): used (by a controller) in conjunction
with other messages, to enable or disable one or more local
controls that have corresponding remote controls.