LTC2872
FuncTion Tables
Table 5. RS485 Driver Mode for a Given Port (485/232 = 1, TE485 = 0)
DXEN
DY
X
CONDITIONS
No Fault
Y
±25kΩ
0
Z
±25kΩ
±
0
±
±
X
0
No Fault
±
No Fault
±
0
X
Thermal Fault
±25kΩ
±25kΩ
Table 6. RS485 Receiver Mode for a Given Port (485/232 = 1, LB = 0)
RXEN
A–B (NOTE 5)
CONDITIONS
No Fault
RA
Hi-Z
0
±
0
0
0
X
X
< –200mV
No Fault
> 200mV
No Fault
±
Inputs Open or Shorted Together (DC)
X
No Fault
±
Thermal Fault
Hi-Z
Table 7. RS485 Termination for a Given Port (485/232 = 1)
TE485
DZ
X
H/F, LB
CONDITIONS
R(A TO B)
Hi-Z
R(Y TO Z)
Hi-Z
0
±
±
X
X
X
X
X
No Fault
No Fault
0
±20Ω
±20Ω
Hi-Z
Hi-Z
±
No Fault
±20Ω
Hi-Z
X
Thermal Fault
Table 8. RS485 Duplex Control for Given Port (485/232 = 1)
H/F
0
RS485 DRIVER OUTPUTS
RS485 RECEIVER INPUTS
Y, Z
Y, Z
A, B
Y, Z
±
Table 9. Loopback Functions for a Given Port
LB
0
RXEN
TRANSCEIVER MODE
X
±
0
Not Loopback
Not Loopback
±
±
Loopback (RA = DY, RB = DZ)
2872f
16
Linear Systems [ Linear Systems ]
