+5V Multiprotocol, Software-Selectable
Cable Terminator
A′
R1
MXL1344A
52Ω
S1
S2
R3
127Ω
A
R5
30kΩ
R8
5kΩ
R6
10kΩ
S3
MXL1543
RECEIVER
R2
52Ω
B′
R7
10kΩ
R4
B
30kΩ
C′
GND
Figure 10. V.28 Termination and Internal Resistance Networks
SERIAL
CONTROLLER
TXD
SCTE
TXC
RXC
RXD
DTE
MXL1543
D1
D2
D3
R1
R2
R3
MXL1344A
TXD
SCTE
MXL1344A
104Ω
104Ω
104Ω
TXC
104Ω
RXC
104Ω
RXD
DCE
MXL1543
R3
R2
R1
D3
D2
D1
SERIAL
CONTROLLER
TXD
SCTE
TXC
RXC
RXD
MXL1544/MAX3175
MXL1544/MAX3175
RTS
D1
RTS
R3
RTS
DTR
D2
DTR
R2
DTR
D3
DCD
R1
DCD
DSR
R2
DSR
R1
D3
DCD
D2
DSR
CTS
R3
CTS
LL
D4
LL
R4
D1
CTS
R4
LL
D4
Figure 11. DTE-to-DCE X.21 Interface
______________________________________________________________________________________ 11