RKC INSTRUMENT Z-TIO-G, Инструкция по эксплуатации

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3. COMMUNICATION SETTINGS
IMS01T28-E4
3-8

RS-485 (2-wire system) send/receive timing
RS-485 communication is conducted through two wires, therefore the transmission and reception of data
requires precise timing.
 Polling procedure
a: Response send time after the controller receives [ENQ] + Interval time
b: Response send time after the controller sends BCC
c: Response send time after the controller receives [ACK] + Interval time or
Response send time after the controller receives [NAK] + Interval time
- - - - -
or
Host
computer
b
c a
- - - - -
N
A
K
A
C
K
E
N
Q
S
T
X
B
C
C
E
O
T
SRZ
Send data
(Possible/Impossible)
Possible
Impossible
Sending status
Send data
(Possible/Impossible)
Possible
Impossible
Sending status

Selecting procedure
a: Response send time after the controller receives BCC + Interval time
b: Response wait time after the controller sends ACK or Response wait time after the controller sends NAK
b a
- - - - -
S
T
X
B
C
C
or
N
A
K
A
C
K
Host
computer
SRZ
Send data
(Possible/Impossible)
Possible
Impossible
Sending status
Send data
(Possible/Impossible)
Possible
Impossible
Sending status
To switch the host computer from transmission to reception, send data must be on line.
The following processing times are required for the controller to process data.
- In Polling procedure, Response wait time after the controller sends BCC
- In Selecting procedure, Response wait time after the controller sends ACK or NAK
 Fail-safe
A transmission error may occur with the transmission line disconnected, shorted or set to the
high-impedance state. In order to prevent the above error, it is recommended that the fail-safe function be
provided on the receiver side of the host computer. The fail-safe function can prevent a framing error from
its occurrence by making the receiver output stable to the MARK (1) when the transmission line is in the
high-impedance state.