Specifications

System Macros Invoked by Drivers
SPI$GET_CONNECTION_CHAR
SPI$GET_CONNECTION_CHAR
Returns characteristics of an existing connection to a specified buffer.
Format
SPI$GET_CONNECTION_CHAR
Description
The SPI$GET_CONNECTION_CHAR macro returns characteristics of an existing
connection to a specified buffer.
The buffer format has the characteristics listed in Table 2–5.
Table 2–5 SPI$GET_CONNECTION_CHAR Macro Buffer Characteristics
Longword Contents
1 Number of longwords in the buffer, not including this
longword. The value of this field must be 10.
2 Connection flags. Bits in this longword are defined as
follows:
Bit Description
0 ENA_DISCON. When set, this bit indicates that
disconnect and reselection are enabled on this
connection.
1 DIS_RETRY. When set, this bit indicates that
command retry is disabled on this connection.
3 Synchronous. When this longword contains 0, the
connection supports asynchronous data transfers; when
it contains a nonzero value, the connection supports
synchronous data transfers.
4 Transfer period. If the synchronous parameter is nonzero,
this field contains the number of 4-nanosecond ticks
between a REQ and an ACK. The default is 64
10
.
5 REQ-ACK offset. If the synchronous parameter is
nonzero, this field contains the maximum number of REQs
outstanding before there must be an ACK.
6 Busy retry count. Maximum number of retries allowed on
this connection while waiting for the bus to become free.
7 Arbitration retry count. Maximum number of retries
allowed on this connection while waiting for the port to win
arbitration of the bus.
8 Select retry count. Maximum number of retries allowed on
this connection while waiting for the port to be selected by
the target device.
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