IEC 60870-5-101 over TCP

The IEC 60870-5-101 driver connects YTCC to RTUs that speak IEC 101, through a TCP connection: a terminal server, a serial-to-Ethernet converter or an RTU with a TCP port. For what all drivers have in common, see How drivers work.

Protocol and role

Role	Controlling station (master). YTCC connects to the RTUs and polls them.
Transport	IEC 101 frames (FT 1.2) over TCP, unbalanced transmission
Port	No default; enter the port of the terminal server or the RTU
Devices per driver	Any number of RTUs, one RTU per host and port
Driver type	IEC 101 (iec101)

Device parameters

Set these on the device in Drivers → devices (see Add drivers and devices). An empty box uses the default shown in it. The help mark next to each parameter shows a short description.

Connection and link

Parameter	Default	Range	Meaning
Transport	— (required)	TCP	Use TCP.
Host	— (required)	IP address or host name	Address of the terminal server or the RTU.
Port	— (required)	1–65535	TCP port.
Serial path, Baud rate, Parity, Data bits, Stop bits	—, 9600, Even, 8, 1	—	For a serial transport; not used with TCP.
Connect timeout (ms)	5000	0 and more	How long the driver waits when it opens the TCP connection.
Reconnect max (ms)	5000	500–600000	Longest wait between two connection attempts; see Reconnecting.
Link mode	Unbalanced	Unbalanced	Use Unbalanced.
Link address	— (required)	must fit Link addr size	Link address of the RTU.
Link addr size	— (required)	1 or 2 bytes	Size of the link address.
Response timeout (ms)	1000	50 and more	How long the driver waits for each answer of the RTU.
Max retries	3	0–10	How often a frame is sent again before the link counts as lost.
Poll interval (ms)	250	10 and more	Pause between class 2 polls when the RTU has no data.
Use link status request	on	on / off	Ask for the link status before resetting the link.
Dir bit, Link test interval (ms), Send single char ack	on, 10000, off	—	For the balanced link mode; not used with Unbalanced.

Application layer

Parameter	Default	Range	Meaning
COT size	— (required)	1 or 2 bytes	Size of the cause of transmission.
CA size	— (required)	1 or 2 bytes	Size of the common address.
IOA size	— (required)	1, 2 or 3 bytes	Size of the information object address.
Common address	the link address	must fit CA size	Common address of the ASDU.
Originator address	0	0–255	Originator address; sent only with a 2-byte COT.

The sizes have no default: take them from the RTU's interoperability list.

Interrogation, counters and clock

Parameter	Default	Meaning
GI on connect	on	Send a general interrogation each time the link comes up. Keep it on.
GI QOI	20	Qualifier of the interrogation: 20 station, 21–36 group 1–16.
GI period (s)	0	Repeat the general interrogation at this interval; 0 is off.
GI timeout (s)	60	How long the driver waits for the end of an interrogation (also of a counter interrogation).
Counter interrogation period (s)	0	Send a counter interrogation at this interval; 0 is off.
Counter QCC	5	Qualifier of the counter interrogation.
Clock sync on connect	on	Set the RTU clock each time the link comes up.
Clock sync period (s)	3600	Repeat the clock synchronisation at this interval; 0 is off.
Clock sync mode	Sequential	Sequential, Once per host or Parallel: how RTUs behind the same host are synchronised.
Time offset minutes	0	Offset of the RTU clock from UTC. For an RTU on Turkish local time, enter 180.

Commands and other

Parameter	Default	Meaning
Cmd timeout (ms)	10000	How long the driver waits for the confirmation of each command step.
Cmd wait termination	off	Count a command as complete only after the activation termination, for all signals of the RTU.
Set invalid on disconnect	on	When the link is lost, mark all signals of the RTU as Bad · Not connected. When off, nothing changes on screen.
Read cmd	on	Ask for the current value of a signal that is added while the driver runs.
Frame log	Off	Off, Asdu or All: write the frames to the driver log, for troubleshooting.

Changing any device parameter except Read cmd reconnects that RTU. Adding, removing or changing signals takes effect without dropping the link and without a new interrogation.

Signal address

Set the address on the Value source tab of the signal, under Address — IEC 101: the IOA, 0–16777215, and it must fit IOA size. In import files, write the number, optionally with IOA in front (see Import and export with Excel or CSV).

The monitoring type is not configured: YTCC takes it from the messages of the RTU. A monitored point and a command point can use the same IOA; incoming data goes to the monitored point.

Monitoring types

Type	Without time	With CP24 time	With CP56 time	Value in YTCC
Single point	1 M_SP_NA	2 M_SP_TA	30 M_SP_TB	On or off
Double point	3 M_DP_NA	4 M_DP_TA	31 M_DP_TB	0 intermediate, 1 off, 2 on, 3 indeterminate
Step position	5 M_ST_NA	6 M_ST_TA	32 M_ST_TB	Integer; Uncertain while in transition
Bitstring of 32 bits	7 M_BO_NA	8 M_BO_TA	33 M_BO_TB	Unsigned number
Measured value, normalised	9 M_ME_NA (21 without quality)	10 M_ME_TA	34 M_ME_TD	−1 to +1
Measured value, scaled	11 M_ME_NB	12 M_ME_TB	35 M_ME_TE	Integer
Measured value, short float	13 M_ME_NC	14 M_ME_TC	36 M_ME_TF	Floating-point number
Integrated totals	15 M_IT_NA	16 M_IT_TA	37 M_IT_TB	Integer; Bad when the counter is invalid

Reading

The driver polls the RTU: class 1 data whenever the RTU reports it has some, otherwise class 2 data, with Poll interval (ms) between empty answers. When the link comes up, it synchronises the clock and sends a general interrogation (if switched on). When the RTU reports a restart (end of initialisation), the start-up sequence runs again.

Commands

A signal can be commanded when its Access is Read / Write or Write only. Its settings are under IEC 60870-5 on the Command tab of the signal:

Setting	Meaning
Command type	Single (C_SC), Double (C_DC), Regulating step (C_RC), Setpoint normalized (C_SE_NA), Setpoint scaled (C_SE_NB) or Setpoint float (C_SE_NC).
Qualifier (0 … 31)	The qualifier of the command (QU), sent as it is.
Select before operate	Send SELECT first and EXECUTE only after the RTU confirms the selection.
Wait for ACTTERM	Report the command as complete only after the activation termination of the RTU.

• For a double command and a regulating step, the value 1 is OFF or LOWER and 2 is ON or HIGHER.
• Each step waits up to Cmd timeout (ms) for the confirmation. A negative confirmation, or causes 44–47, rejects the command with the reason.
• A command must reach the RTU within 2 seconds of being sent. With select before operate, the EXECUTE step also has to go out within these 2 seconds, otherwise the command ends as expired.
• The RTU accepts one command at a time; a second command is rejected as Previous command in progress. If the link is down, the command is rejected at once.

For how operators send and confirm commands, see Send commands.

Quality mapping

Quality descriptor of the RTU	Quality in YTCC
IV (invalid) or BL (blocked)	Bad
SB (substituted)	Good · Substituted, value origin manual in the field
NT (not topical)	Uncertain · Stale (last usable)
OV (overflow)	Uncertain · EU exceeded
none	Good

When the link is lost, the signals are marked Bad · Not connected and keep their last value; after the link comes back, the general interrogation refreshes them. With Set invalid on disconnect off, the signals keep Good with an old value; keep it on.

Time tags

Time tag	Time in YTCC
CP56Time2a, valid	The RTU time; time source device
CP24Time2a (minutes and milliseconds)	Date and hour are taken from the arrival time
Invalid bit set, impossible date, more than 5 minutes ahead or 7 days behind	Arrival time; device time invalid
No time tag	Arrival time; protocol carries no time

YTCC converts RTU times to UTC with Time offset minutes. The clock synchronisation sends UTC plus the same offset.

Reconnecting

After the link is lost, the driver opens it again after 100 ms and doubles the wait (0.1, 0.2, 0.4, 0.8, 1.6, 3.2 s …) up to Reconnect max (ms), 5 seconds by default. After a cable is plugged back in, the RTU is connected again within about 10 seconds with the defaults.

Diagnostics

Read now on the Value source tab sends a read command for the IOA and waits 2 seconds:

Text	Meaning
A type and value	The RTU answered
Not connected — … ; IOA … was not read	The link to the RTU is down
Timeout — no response from … within 2000 ms	The RTU did not answer the read command
RTU refused read command C_RD_NA_1 — unknown information object address (COT 47) …	The IOA does not exist in the RTU
Link failed before the answer — …	The link dropped during the read

Symptom	Likely cause
The RTU does not start	Transport is not TCP, Link mode is not Unbalanced, missing sizes, or a second RTU on the same host and port
Connected, but no values	Wrong Link address, Common address or sizes; GI on connect off
Values arrive slowly	Poll interval (ms) or Response timeout (ms) too long; a slow line behind the terminal server
Times wrong by hours	Wrong Time offset minutes
Command expired with select before operate	The RTU confirms SELECT too slowly for the 2-second limit

Set Frame log to Asdu or All to see the frames in the driver log; set it back to Off afterwards.

Interoperability

Monitoring direction

Type	Supported
1, 3, 5, 7, 9, 11, 13, 15, 21 without time tag	Yes
2, 4, 6, 8, 10, 12, 14, 16 with CP24 time tag	Yes
30–37 with CP56 time tag	Yes
70 end of initialisation	Yes (start-up sequence repeats)

Control direction

Type	Supported
45 C_SC, 46 C_DC, 47 C_RC, 48 C_SE_NA, 49 C_SE_NB, 50 C_SE_NC	Yes, with select before operate

System commands

Command	Supported
100 C_IC general interrogation (station and groups)	Yes
101 C_CI counter interrogation (periodic)	Yes
102 C_RD read	Yes
103 C_CS clock synchronisation	Yes

Link layer

Function	Supported
Unbalanced transmission	Yes
Reset of remote link, request status of link	Yes
Request user data class 1 and class 2, ACD and DFC	Yes
Single character E5 as acknowledgement	Received