
3
Date Code 20200326
SEL Application Guide 2020-04
RMB
y
FL
f
M
IRRORED
B
ITS
RMB Channel Fail
Status
g
User-defined value transmitted when ROK = 0.
RMB
y
PU
M
IRRORED
B
ITS
RMB Pickup
Debounce Messages
1
Number of received messages before RMB
y
picks up.
RMB
y
DO
M
IRRORED
B
ITS
RMB Dropout
Debounce Messages
1
Number of received messages before RMB
y
drops out.
a
If PROTO = MBGA or MBGB, the RX_ID and TX_ID settings move from Port settings to Group settings. The MB8 protocol
option is not available in the SEL-421-5 relay, but if the relay is communicating to another relay with MB8 protocol, set
PROTO = MBA or MBB, and set STOPBIT = 2. See [4] for further information.
b
When you use a fiber-optic cable for communications, consider using the maximum baud rate of 38400.
c
x
= A or B.
d
The TXMODE setting provides compatibility with SEL devices that are not SEL-400 series relays. The SEL-421-5 sends
messages faster than SEL-300 series relays and other SEL devices can process the messages. This can lead to loss of data
and a failure to communicate properly. When you set TXMODE to P, the relay sends new M
IRRORED
B
ITS
messages every 3 ms
even if the selected data speed (SPEED setting) allows more frequent messages.
e
P stands for Paced mode. Paced mode provides speed compatibility. This setting must be P for connections to devices that
are not SEL-400 series relays.
f
y
= 1 to 8.
g
To maintain security during a loss of communications in a POTT scheme, you can set the default state of the permissive
receive bit (RMB1A) to
0
, thus RMB1FL = 0. In a DCB scheme, you can set the default state of the block bit (RMB1A) to
1
, thus
RMB1FL = 1.
Table 2
SEL-311C-1 Port 2 Settings (For Communications Between SEL-421-5 and SEL-311C-1 Relays)
(Sheet 1 of 2)
Setting
Setting Description
Setting Value
Comment
EPORT
Enable Port
Y
The port must be enabled to set up communications.
PROTO
Communications Protocol
MBA
a
Enable M
IRRORED
B
ITS
communications on
Channel A.
SPEED
Communications Baud Rate
9600
b
The SEL-311C-0 is limited to 38400, and the
SEL-311C-1, -2, -3 are limited to 57600.
RTSCTS
Enable Hardware Handshaking
N
Not needed for relay-to-relay communications.
TXID
M
IRRORED
B
ITS
Transmit Identifier
1
Must match the receive identifier of the remote
relay.
RXID
M
IRRORED
B
ITS
Receive Identifier
2
Must match the transmit identifier of the remote
relay.
RBADPU
M
IRRORED
B
ITS
Receive Bad Pickup
Time
60 (default)
A channel error must last 60 seconds before
RBAD
x
c
asserts.
CBADPU
PPM M
IRRORED
B
ITS
Channel Bad
Pickup
1000 (default)
CBAD asserts if the ratio of channel downtime to
total channel time exceeds this value.
RXDFLT
M
IRRORED
B
ITS
Receive Default
Status
XXXXXXXX
d
The default state in place of received data in an
error condition.
Table 1
SEL-421-5 Port 2 Settings (Sheet 2 of 2)
Setting
Setting Description
Setting
Value
Comment