Mitsubishi Electric MELSEC-KOJIU Instruction Manual page 70

J
5 . EXPLANATION OF PROGRAM
Shift register (30 bits)
I '
Bit No. 1 ~ 2 9 28 27
3
2 1
0
63 62 61 60' M91
90
89
88
87
/Head No.
59 58
1) Shift command should be converted into pulses, otherwise "racing" (shift goes on
without interruption although only one pulse is given) might occur.
2) When only one shift register is available in a program, it is recommended to enter the
data (head No., number of bits, etc.) at
start
of execution, thereby "B" block may be
simplified with only Mn and F114.
3)
Actual shift register requires, in addition to the circuit shown in Fig. 5.4.6.1, reset cir-
cuit and data set circuit. For details, refer to para 5.4.6.2.
4) One-bit shift occurs each time when Mn turns on.
(5) The status of the shift register exemplified in Fig. 5.4.6.1 is as follows:
1) Leftward shift
1
-
/ / /
I
1
4 4
60 59 58
- - -
- -
M91 90
/
4
1 1 0 1 1 1 0 1 0 1 1
I
' ~ L -
I
L
4
After execution
(After shifting)
Content of M89 is not shifted,
and M90 remains unchanged.
Content of M59 is not shifted,
and M60 always turn to "0".
Fig. 5.4.6.2 Left ward Shift
2) Rightward shift
Shift register (30 bits)
Before execution
After execution
(After shifting )
Content of M90
is
not shifted,
and M89 always turns
to
"0".
kontent of M60 is not shifted,
and M59 remains unchanged.
Fig. 5.4.6.3 Rightward Shift
a) In leftward as well as rightward shift, the first bit (M60 for leftward shift, and M89 for
rightward (shift) is not affected by shifting, and replaced with "0" a t all times. If any
shift data must be entered,
it
should be placed after the shifting.
b) The contents a t the final bit of the shift register (M89 for leftward shift, and M60 for
rightward shift) is erased due to overflow.
(6) Any bit "Mn" in the shift register may be set or reset with set (SET) instruction or reset
(RST) instruction.
62