------------------------------------------------------HMCS46C,HMCS46Cl
• REGISTER
The
HMCS46C
has eight 4-bit registers and two I-bit registers
available
to
the programmer. The I-bit registers
are
the Carry
F/F
and the Status F/F. They are explained in the following
paragraphs.
• Status
F/F
(S)
The Status F
/F
latches the result
of
logical or arithmetic
operations (Not Zero, Overflow) and bit test operations. The
Status
F/F
affects conditional instructions (LPU,
BR
and CAL
instructions). These instructions are executed only when the
Status F
/F
is
"1".
If
it
is
"0",
these instructions are skipped and
the Status
F/F
becomes
"1".
• Accumulator (A; A Register) and Carry
F/F
(C)
The result
of
the Arithmetic Logic Unit (ALU) operation (4
bits) and the overflow
of
the ALU are loaded into the accumula-
tor and the Carry F/F. The Carry
F/F
can be set, reset or tested.
Combination
of
the accumulator and the Carry
F/F
can be right
or left rotated. The accumulator is the main register for
ALU
operation and the Carry F
/F
is
used
to
store the overflow gener-
ated by ALU operation when the calculation
of
two or more
digits (4 bits/digit)
is
performed.
• 8 Register (8)
The result
of
ALU operation (4 bits)
is
loaded into this
register. The B register
is
used
as
a sub-accumulator
to
stack
data temporarily and also used
as
a counter.
• X Register (X)
The result
of
ALU operation
(4
bits)
is
loaded into this
register. The X register has exchangeability for the
SPX
register.
The X register addresses the
RAM
file.
• SPX Register (SPX)
The
SPX
register has exchangeability for the X register.
The
SPX register
is
used
to
stack the X register and expand
the addressing system
of
RAM
in combination with the X
register.
• Y Register (Y)
The result
of
ALU operation
(4
bits)
is
loaded into this
register. The
Y register has exchangeability for the
Spy
register.
The
Y register can calculate itself simultaneously with transfer-
ring data by the bus lines, which
is
usable for the calculation
of
two or more digits (4 bits/digit). The Y register addresses the
RAM
digit and I-bit Discrete I/O.
•
Spy
Register
(Spy)
The
Spy
register has exchangeability for the Y register. The
Spy
register is used
to
stack the Y register and expand the
addressing system
of
RAM
and I-bit Discrete I/O in' combina-
tion with the Y register.
The Data
I/O Registers R4 and R5, which are not connected
to
the
LSI
pin; can be used for general purpose registers.
• R4 Register (R4)
The contents
of
the accumulator and the B register are trans-
ferred by LRA and LRB instructions, respectively. The con-
tents
of
the R4 register are sent
to
the accumulator and the B
register
by
LAR and LBR instructions, respectively.
•
R5
Register (R5)
The contents
of
the accumulator and the B register are trans-
ferred by LRA and
LRB
instructions, respectively. The contents
of
the
R5
register are sent
to
the accumulator and the B register,
respectively.
• INPUT/OUTPUT
• 4-bit Data
Input/Output
Common Channel (R)
The
HMCS46C
has four 4-bit Data I/O Common Channels
(RO,
RI,
R2
and R3).
The
4-bit registers (Data I/O Register) are attached
to
these
channels.
Each channel
is
directly addressed by the operand p
of
input/output instruction.
The data
is
transferred from the accumulator and the B
register to the Data
I/O Registers
RO
to
R3
via
the bus lines.
Pattern instruction enables the patterns
of
ROM
to
be loaded
into the Data
I/O Registers R2 and R3.
Input, instruction enables the
4-bit data
to
be sent
to
the
accumulator and the B register from
RO
to
R3. Note that, since
the Data
I/O Register's output
is
directly connected
to
the pin
even during execution
of
input instruction, the input data
is
wired logic
of
the Data I/O Register's output and the pin input.
Therefore, the Data
I/O Register should be set
to
15
(all bits
of
the Data I/O Register
is
"1")
not to affect the pin input
before execution
of
input instruction, and Open Drain or With
Pull up
MOS
should be specified for the I/O configuration
of
these pins.
97
The block diagram
is
shown in Figure 14. The I/O timing
is
shown in Figure 15.
• 1-bit Discrete
Input/Output
Common Terminal (D)
The
HMCS46C
has 16 I-bit Discrete I/O Common Terminals.
The
I-bit Discrete I/O Common Terminal consists
of
a I-bit
latch and an
I/O common pin.
The
I-bit Discrete I/O
is
addressed
by
the Y register. The
addressed latch can be set or reset
by
output instruction and
"0"
and
"1"
level can
be
tested with the addressed pin by input
instruction.
Note that, since the latch output
is
directly connected
to
the
pin even during execution
of
input instruction, the input data
is
wired logic
of
the latch's output and the pin input. Therefore,
the latch should be set
to
"1"
not
to
affect the pin input before
execution
of
input instruction and Open Drain or With Pull up
MOS
should
be
specified for the I/O configuration
of
this pin.
The
Do
to
D3
terminal are also addressed directly by the
operand n
of
input/output instruction and can be set or reset.
The block diagram
is
shown in Figure
16
and the I/O timing
is
shown in Figure 17.
• I/O Configuration
The I/O configuration
of
each pin can be specified among
Open Drain, With Pull up
MOS
and
CMOS
using a mask option
as
shown in Figure 18.
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