RS-232
An RS-232 Interface section
is
part
of
the
processor
board's
electronics. Using
an
INS8250
UART,
it's
almost identical
to
the
HP
98644A RS-232 Serial Interface Card.
The
processor
board's
RS-232 differs from
the
HP
98644A Interface
Card
in
that
it:
• Allows
interrupts
at
level 5 only.
There
are no switches
to
change
the
interrupt
level is
the
same as
the
HP
98644 Card.
•
Permanently
sets
the
select code
to
9.
The
HP
98644
card
has switches which allow
this
address
to
be
changed.
• Does
not
allow reconfiguration
to
change
the
RS-232's ID
to
that
of
the
HP
98626 card.
Two switches on
the
98561-66511
board
are associated with RS-232.
They
perform
the
following
functions:
• Controls
the
local/remote
bit
in
the
ID register.
• Sets
the
handshake
input
lines
to
their
default condition, all ones.
In
addition
to
the
registers built into
the
INS8250 UART, two
external
register have also been
implemented.
Both
sets of registers are
multi-mapped
within a 64 K-byte region
of
memory
associated with
I/O
select code
9.
HP-IB
Interface
Hewlett-Packard Interface Bus (HP-IB)
is
HP's
version
of
the
IEEE
488 interface
standard.
HP-IB
on
this
processor
board
is much like
HP-IB
implementations on
other
HP
9000 Series
200 computers.
It
uses a TMS9914 HP-IB controller which allows
data
transfer
rates
up
to
450 K-bytes/second.
The
TMS9914
is
a memory-mapped
I/O
device which
is
multiple-mapped
within a 64 K-byte internal
I/O
device.
Two registers control
hardware
which can generate
an
interrupt
as a result
of
a
HP-IB
device
responding
to
a parallel poll.
It
has
the
ability
to
generate
an
interrupt
from a parallel poll
response. For
this
feature, two registers external
to
the
TMS9914 are used.
These
registers are
in
addition
to
the
two
external
registers
that
exist for internal HP-IB interfaces in
other
Series
200 computers.
All registers associated with
the
HP-IB
are multiple Inapped within a 64 K-byte block
of
memory
in
the
internal
I/O
address range.
Information on
the
TMA9914A
and
its registers
can
be
found in
the
'TMS9914A General
Purpose
Interface Bus
(GPIB)
Controller'
Data
Manual.
46
Functional Description
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