IC-Module for EtherNet/IP
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shift register modules read in at the positive edges of the input
values. From there, they are shifted bit by bit to the SSC input
register area of the KUNBUS-IC during the current cycle.
The clock rates of the IC-Modul
e
can be adapted manually or
automatically in 3 levels and are about 300, 1200 or 4800 Kbit/s. The
load impulse is between 5 and 15 µs long (active low). The delay
between the load edge (positive edge of the load impulse) and the
first clock edge (from high to low) is between 1 and 2 µs. These
values are completely uncritical when using the shift register modules
74HC165 (Input) and 74HC594 (Output).
An optional SSC RESET line initialises the shift register modules
during the starting process of the IC-Modul
e
(i.e. also during each
reset of the module).
With an arrangement of the output and input shift register as shown
in this example, all registers are switched in series so that the
KUNBUS-IC has its own output data shifted back into the input
register again for checking purposes. A test sample shifted through
the complete chain without a LOAD signal allows the KUNBUS-IC to
detect how long the entire chain is by means of the necessary clock
signals for such a shifting procedure.
A centre pickoff between the output and input modules allows the
KUNBUS-IC to also detect the corresponding number of inputs and
outputs of the shift register modules during this run of a test sample.
If bit errors occur, the clock rate is reduced in automatic mode by one
level. Hence, with such a structure the KUNBUS-IC can find the right
setting for the chain lengths and maximum possible transmission rate
independently. It is also possible, however, to assign the lengths and
clock rates manually via the CDI menu. In this case, the centre
pickoff can also be omitted (it is only needed for determining the
allocation between inputs and outputs of the shift register modules).
The entire chain length is monitored constantly during ongoing
operation and must match the configured length. If the module
detects a difference, then it shuts down the SSC communication and
reports an error status via its status register.
The KUNBUS-IC can operate a maximum of 32 shift registers. You
can use these freely as input and output shift registers.
Note on cycle time: The cycle time of the shift register interface is
normally independent of its chain length since the KUNBUS-IC in its
work cycle only starts the transmission of a shift procedure. The shift
procedure itself then takes place independently of the work cycle of
Components
