PCC-IV Instruction Manual (Rev. 0.1)
Page 6-36
Section 6
– Blockware Functions
Technical Reference
F97
[RDIN] (MODBUS) Remote Discrete Input
When the PCC-IV MODBUS communications link (Comm Link) is in "Local Mode", the Comm Link can read all
Block Outputs; however, the Comm Link is prevented from writing data to (i.e. changing) all Block Outputs, except
for the
RAIN
and
RDIN
Blocks. The Comm Link is always permitted to write data to
RAIN
and
RDIN
Block Outputs.
Pulse Mode = Off (i.e. Parameter 1 = 3600 sec): The value written
by Comm Link remains in effect until a new value is written by
Comm Link, or until a Comm Link time-out. Upon Comm Link time-
out (i.e. no new Comm Link writes within (Parameter 2) seconds),
the Comm Link value can either remain at the last value received
or switch to the default value (see parameters 3 & 4).
Pulse Mode = On (i.e. Parameter 1 < 3600 sec): The
RDIN
Block
Output becomes a re-triggerable one-shot pulse, with (Parameter
1) seconds minimum duration. If Parameter 1 = 0 seconds,
RDIN
creates a one scan long pulse. Pulse mode is useful as a Comm
Link Watchdog timer, or for logic that requires momentary pulses.
A Comm Link write of "0" followed by a Comm Link write of "1" is
the "trigger" to change the
RDIN
Output to a "1" and start the
Pulse timer. If no additional Comm Link triggers occur, the
RDIN
Output changes to a "0" after the Pulse timer
expires. If another Comm Link trigger occurs when
RDIN
's Output = "1", the timer restarts. If no further Comm Link
writes occur, or if Comm Link continuously writes either a "1" or a "0", the Pulse timer will expire, and the
RDIN
output changes back to a "0". See Pulse Mode timing diagram below:
Power Down: The Block Output is saved in the Retentive Memory area of the NVRAM.
CPU start-up: If Pulse Mode=Off: The Block Output and the Comm Link value are set to the value in Retentive
Memory during the first scan. If Retentive Memory is invalid, the Block Output initializes to the Default Output upon
CPU start-up. If Pulse Mode=On: The Block output is set to "0", and Comm Link must write a "0", followed by a "1"
to change the
RDIN
Output to a "1".
---------------------------------------------------------------------------------------------
NAME: RDIN SINGLE USE FUNCTION: N OUTPUT TYPE: D
---------------------------------------------------------------------------------------------
No Inputs
Parameter Description Default Max Min Code Notes
_____________________________________________________________________________________________
1 PULSE SECONDS
(3600=CONTINUOUS) 3600 3600 0 2 1
2 COMM FAIL DELAY SEC. 5 3600 1 2 x
3 FAIL ACTION 0=LAST, 1=DEFAULT 0 1 0 2 x
4 FAIL DEFAULT 0 1 0 2 x
Notes:
1. If Pulse Seconds less than 3600, Fail delay must be greater than Pulse seconds.
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
0
5
10
15
20
25
Seconds
Comlink Writes
RDIN Output
