Hitachi MB-6890, Руководство по обслуживанию

Страница: 17 / 123

*
Enable(E)
The Enable signal,E, is
a
high impedance TTL compatible
input that
the bus
input/output data buffers and clocks
data
to
and from
the
ACIA.
*
Read/Write(R/W)
The
R/W
line is
a
high impedance input that is
TTL compatible and
is
used
to
control the direction
of data flow
through the ACIA’s
input/output data bus interface,
When R/W is
High(MPU Read cycle),
ACIA
output
drivers
are
turned
on
and
a
selected
register
is
read.
when it is
Low,the ACIA
output
drivers
are
turned off and the
MTU
writes into
a
selected
register. Therefore, the
R/W signal is used
to select read
only
or
write
only registers within the
ACIA.
* chip
Select(CSO,CSl
552)
These three high impedance
TTL compatible input lines
are
used
to
address
the
ACIA. The
ACIA
is
selected when
CSO andCS1 are
High
and
CS2
is
Low.
*
Register
Select(RS)
The RS line is
a
high impedance input that is
TTL compatible.
A High level is used
to
select the
Transmit/Receive
Data Registers
and
a
Low level the
ControVStatusRegisters.
The R/W
signal
line
is used in
conjunction
with
Register Select
to select the
read
only
register in each
register pair.
*
Interrupt
Request(TR5)
IRQ
is
a
TTL compatible,open drain(no
internal_pullup),active
Low
output
that is used
to interrupt the
MPU.
The
IRQ
output
remains
Low
as
long
as
the
cause
of the
interrupt
is
present
and the
app-
ropriate
enable
within
the
ACIA
is
set.
*
Clock
INputs
Separate
high impedance
TTL compatible inputs
are
provided
for
clocking
of transmitted
and received
data. Clock
frequencies
of l, 16
or
64 times
the data
rate
may
be
selected.
*
Transmit Clock(Tx CLK)
The
Tx CLK input is used for the
clocking of transmitted
data.
The transmitter initiates data
on
the
negative transition of
the clock.
*
Receive
Clock(Rx CLK)
The Rx CLK
input
is
used for synchronization
of
received
data.
(In
the
Ø
l mode, the clock
and data must be
synchronized
extern-
ally.) The receiver
samples
of the
data
on
the
positive transition
of the
clock.
*
Serial
Input/Output Lines
*
Receive Data(Rx
Data)
The
Rx Data
line is
a
high
impedance TTL compatible
input through
which data is received
in
a
serial
format. Synchronization with
a
clock for detection
of data is
accomplished internally when clock
rate
are
in the
range
of O
to
SOO
kbps when external
synchroniza-
tion is utilized.
*
Transmit
Data(Tx Data)
The
Tx Data
output
line’transfers
serial
data to
a
modem
or
other
peripheral.
Data rates
in
the
range
of O
to
500
kbps when external
synchronization is utilized.
N
T5
enables