Intel MCS48 User Manual page 355

8278
8278
COMMANDS
The
8278 operating
mode
is
programmed
by
the
master
CPU
using the
Ao,
WR,
and D0-D7
inputs as
shown
below:
A
.CS
INVALID
X
X
Where
Al indicates
Auto Increment and A3-A0
is
the
address
of
the next display character
to
be read
out.
Al=1
AUTO
increment
Al=0 no
AUTO
increment
Write Display
Command
1
Al
A3 A
2
A1
Ao
\-f
XHX
The
master
CPU
presents the proper
command
on
the Do-
D7
data
lines
with
Ao=1 and
then
sends
a
WR
pulse.
The
command
is
latched by the
8278 on
the
rising
edge
of the
WR
and
is
decoded
internally to set the proper operating
mode.
COMMAND SUMMARY
Keyboard/Display
Mode
Set
N
E
I
D K
where
the
mode
set bits
are defined as
follows:
K
—
the
keyboard
mode
select
bit
—
normal key entry
mode
1
—
special function
mode:
Entry on key
closure
and on
key
release
D
—
the display entry
mode
select
bit
—
left
display entry
right display entry
the interrupt
request (IRQ) output enable
bit.
enable
IRQ
output
disable
IRQ
output
E
—
the error
mode
select
bit
—
error
on
multiple
key depression
1
—
no
error
on
multiple
key depression
N
—
the
number
of display digits select
0—16
display digits
1—8
display
digits
NOTE:
The
default
mode
following a
RESET
input
is all
bits
zero:
1
—
I
—
—
1
—
Read
F
IFO
Command
CODE
1
Read
C display
Command
CODE
1
1
Al
A3
A
2
Ai Ao
Where
Al indicates
Auto Increment and A3-A0
is
the
address
of
the next display character
to
be
written.
Clear/Blank
Command
1
1
UD BD CD
CF CE
Where
the
command
bits
are defined as
follows:
CE =
Clear
ERROR
CF =
Clear
FIFO
CD =
Clear Display
RAM
to
all
High
BD =
Blank Display
to
all
High
(Display
RAM
unaffected)
UD =
Unblank
Display
The
display
is
cleared
and
blanked following a Reset.
8278
Status
Read
The
status register
in
the
8278 can be
read
by
the
master
CPU
using the
Ao,
RD, and D0-D7
inputs as
shown
below:
A
,C3
X X
\ /
The 8278
places
8-bits of status
information on
the
D0-D7
lines
following
(Ao,
CS,
RD)
=
1,0,0
inputs
from
the
master.
Status
Format
S3 s
2
Si
So
B KE
1
IBFlOBF
D
7
D
6
D
5
D
4
D
3
D
2
D,
D
Where
the status
bits
are defined as
follows:
OBF
=
Output
Buffer
Full
Flag
IBF
=
Input Buffer
Full
Flag
KE =
Keyboard
Error Flag
(multiple depression)
B
= BUSY
Flag
S3-S0
=
FIFO
Status
8-65
00227A