Radio Shack Telephone Interface II Technical Manual

NATIONAL
MM2316
ROMS
The
National ROMs
were the
second type of ROM
the
factory received
during
production. These ROMs
were used
in
a
large
number
of "D" level Boards
and in
a
few
"A"
level Boards. These
devices
are true Read Only
Memories
since they
are not
programmable (except
by the vendor),
nor are they
eraseable. They may
be identified
by the
colored
ceramic
package
(only
a few)
or in 24
pin dual-in-
line
plastic packages.
The ceramic
packages
have the part
number MM2316
followed by
either an "R/D"
or an
"S/D". The
"R/D" is ROM
A and the
"S/D" is ROM B.
The
plastic packaged ROM
has the
part number
"M2316E"
and below
it "MMS258ET"
followed
by an
"
R/N"
or an
"S/N".
Once again,
the
77
R7N" is ROM A,
while the "S/N"
is
ROM
B. These
ROMs may be
in either Z33
or
Z34
socket
and still
operate correctly. In
other words, ROM A
does not
have
to
be
in socket Z33.
It could be
in socket. Z34,
and
vice versa
for ROM
B.
The
reason
you need
to
know
the
differences
between ROM
A
and
ROM
B is in trouble-
shooting. Certain
software
troubleshooting aids
may fail
ROM A
and pass ROM B. You
need
to identify ROM A
to
replace it
or
for
further
troubleshooting.
The "D" level
Board with
National ROMs
will usually
have
only two
wire modifications
or jumpers,
directly
under the
ROM
sockets. These jumpers
will also have
two
etch
cuts associated
with them.
"A" level Boards
using
National ROMs
may have
more jumpers. This
is because
an
"A" level
Board
may have
been modified
to
use Intel
EPROMs
and then later
remodified
to accept the
National
ROMs. Be
careful
when identifying
the different
Board
levels.
The
two wire modifications
associated
with National
ROMs
are
shown
in
Figure 15. Notice
that only
two wires
are switched
around. There
are no spare
gates
used
in this
modification.
MOTOROLA 7800
SERIES ROMS
(TWO
CHIP SET)
either
Z33
or Z34, but it's
usually put in
Z33.
Once again,
there
are no
PCB
modifications. Notice the
part
number on
the single chip
ROM
and the
7809
ROM B mentioned
above. Be very careful when
replacing
ROMs.
A11
ROM*
Figure
15. National
ROMs
in "D" Level
Board*
*NOTE:
The only differences
between
the Schematic
on
this page and the
Master Schematic
are that
A1
1
is
on Pin 20
and ROM* is
on
Pin
18.
Motorola
was the next
vendor
to supply ROMs for
the
TRS-80. These
ROMs may
be identified
by the
part number
7807
for ROM
A and
7804 for ROM B.
These
devices are
used
only on "D"
level Boards
and there
are no
PCB
modifications.
As with National
ROMs,
Motorola ROMs
may be placed
in either Z33's
or Z34's
socket.
BASIC
II
ROMS
MOTOROLA
7800
SERIES ROMS
(SINGLE
CHIP SET)
The last
ROM
supplied
to the factory
was a single
Motorola
ROM. It
may
be packaged
in either ceramic
(like
a
few
of
the National's)
or in plastic.
The device's
number is
"7809"
and
also
says
"BASIC
I". This
chip may
be inserted in
The TRS-80
having BASIC II
ROMs
are easily
identified.
There
are no
ROMs
plugged
into Z33
or
Z34.
Instead,
there
is a flat ribbon
cable interconnecting
the
GPU
Board
to
a
small 4-chip ROM
Board. This
ROM Board
is stuck, using
double-sided
tape, to the etched
side
of the
CPU
Board.
The three ROMs
on this Board contain
BASIC
II. These
ROMs
may be
supplied by
various
vendors.
Figure
16 is
the Level
II BASIC
Schematic.
35

Radio Shack Telephone Interface II Specifications

General

Brand	Radio Shack
Model	Telephone Interface II
Category	Desktop
Language	English