(
(
(
I/O
Data
Flow
Control
The controller receives data from the
I/O
devices on the
9-bit
(8 data, 1 parity) bus
in
from the base
I/O
card.
Data
is
sent
to
the
I/O
devices on the
9-bit
bus out
to
the base
I/O
card. The control, put, and get strobe
pulses and the
'op
code E tag' line signal the
I/O
devices when
I/O
microinstructions are executed.
The control strobe
has
two
purposes.
It
identifies the
data on the data bus out
as
control data, and it also
serves
as
a timing pulse
to
indicate
to
the
I/O
device
exactly when the bus out data is valid.
The put strobe also has
two
purposes. Besides serving
as
a timing pulse, it indicates that the data bus out
contains data
for
a put instruction.
The get strobe signals the
I/O
device that the data
placed on the data bus in by the device was sampled by
the controller.
The op code signal
is
a decode
of
the get byte
microinstruction. The get byte microinstruction (op code
E)
occurs '!IIeli before the get strobe and is used
to
transfer data. The logical get microinstruction (op code
0)
is
used
to
transfer status. The timing relative
to
the
strobe identifies the type
of
information that has been
requested.
Read
Only
Storage
Read
Only Storage
(ROS)
contains programs and data
used to control the 5100 computing system.
Executable
ROS
Executable
ROS
provides rapidly accessible resident
storage
for
frequently used programs. The BASIC,
I/O,
and diagnostic (H2) cards and the APL supervisor (H4)
card house the executable
ROS
in
the 5100 Portable
Computer.
The controller
(G2)
card addresses executable
ROS
via
the storage address bus (SAB). The 16 SAB bits are
represented by 0123 4567 89AB
CDEF.
Bit 0 is the card
select bit. a down level selects the APL supervisor (H4)
card, and
an
up level selects the BASIC,
I/O,
and
diagnostic (H2) cards. Bits 123 4 select one
of
the 16
chips
on
each card. Bits 567 89AB
CDE
select the
address location on the chip. Bit F is not used because
each microinstruction
is
fetched
as
a halfword
(2
bytes)
and
an
even-odd pair
of
bytes is fetched.
Executable
ROS
contains no data other than
microinstructions.
ROS
Control Lines
Executable
ROS
APL Executable
H2
Storage
Read
Bus
ROS,
Storage
Address Bits
H4
APL
ROS
C2,D2,D4
Interrupt
ROS
~
R/W
Storage
Controls
Control
K2, K4, L2, L4,
Address
Bits
Lines
M2, M4, N2, N4
Bits,
and
Controls
f--
Storage
I/O
-1
Write
I/O
Control
Bus
Common
and
~ontrol
Lines
Lines
-
Controller
Base
I/O
Language
ROS
Bus
In Bits
F2
Bus
In Bits
G2
aus
Out Bits
Bus
Out Bits
-
Data
E2
Device
Device
Address
Bits
Address Bits
Data
B
its'
Address
Bits
-
and
Controls
•
,
Basic
ROS
C4
Controller 4-19
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