Sun Microsystems Sun PCI High Speed Quad Port Serial Interface Adapter 819-1207-11 - Manual (Page 52)

32 Sun PCI High Speed Quad Port Serial Interface Adapter User’s Guide • May 2010
FIGURE B-1 illustrates a synchronous null modem cable that allows you to connect
two Sun systems that each supply clocking, using the RS-449 interface. Each Sun
supplies clocking on pins 17 and 35. The null modem cable routes this clocking to
pins 8 and 26 on the opposite side to provide receive clocking.
Because the RS-449 interface is balanced, there are two pins for each signal. For
example, Transmit Data (TxD), pins 4 and 22, is connected to Received Data (RxD),
pins 6 and 24. This means that pin 4 is connected to pin 6 and pin 22 is connected to
pin 24.
FIGURE B-1 Null modem Cable (Both Suns Supply Clocking)
TxD (4,22)
RxD (6,24)
RTS (7,25)
CTS (9,27)
DSR (11,29)
SG (19)
DCD (13,31)
RxC (8,26)
DTR (12,30)
TxC (17,35)
Sun workstation
TxD (4,22)
RxD (6,24)
RTS (7,25)
CTS (9,27)
DSR (11,29)
SG (19)
DCD (13,31)
RxC (8,26)
DTR (12,30)
TxC (17,35)
Sun workstation