29
29
the Status Register during Command Chaining
operation.
The Status Register defaults to the
value 1XX1 0001 upon either hardware or
software reset.
Diagnostic Status Register (Location +01Hex)
The Diagnostic Status Register contains seven
read-only bits which help the user troubleshoot
the
network
or
node
operation.
Various
combinations of these bits and the TXEN bit of
the Configuration Register represent different
situations. All of these bits, except the Excessive
NAK bit and the New Next ID bit, are reset to
logic "0" upon reading the Diagnostic Status
Register or upon software or hardware reset.
The EXCNAK bit is reset by the "POR Clear
Flags" command upon software or hardware
reset. The Diagnostic Status Register defaults to
the value 0000 000X upon either hardware or
software reset.
Command Register (Location +01Hex)
Execution
of
commands
are
initiated
by
performing write operations to this register. Any
combinations of written data other than those
listed in Table 8 are not permitted and may result
in incorrect chip and/or network operation.
Address Pointer Registers (Location +02Hex,
+03Hex)
These read/write registers are each 8-bits wide
and
are
used
for
addressing
the
internal
ARCNET RAM. New pointer addresses should
be written by first writing to the High Register and
then writing to the Low Register because writing
to the Low Register loads the address.
The
contents of the Address Pointer High and Low
Registers are undefined upon hardware reset.
Configuration Register (Location +06Hex)
The
Configuration
Register
is
a
read/write
register which is used to configure the different
modes of the ARCNET core. The Configuration
Register defaults to the value 0001 1000 upon
hardware reset only.
Setup Register (Location +07Hex)
The Setup Register is a read/write 8-bit register
accessed when the Sub Address Bits are set up
accordingly
(see
the
bit
definitions
of
the
Configuration Register).
The Setup Register
allows the user to change the network speed
(data
rate)
or
the
arbitration
speed
independently, invoke the Receive All feature,
change the nPULSE1 driver type, and reduce
protocol timeouts by a factor of 3. The data rate
may be slowed to 156.25 Kbps and/or the
arbitration speed may be slowed by a factor of
two. The SLOWARB must be set to a 1 for the 5
Mbps operation. The Setup Register defaults to
the value 0000 0000 upon hardware reset only.
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