HSSI Null Modem Cable
HSSI Null Modem Cable
The null modem cable (CAB-HNUL=) can connect two routers directly back to back. The null modem cable is 10-feet (3.048 meters) long. Figure 1-6 shows the null modem cable. The maximum null modem cable length allowed is 50 feet (15.24 meters). The two routers must be in the same location and can be two Cisco 7000 series routers, two Cisco 7500 series routers, two Cisco 7200 series routers, two Cisco uBR7200 series routers, or any combination of each. A null modem connection allows you to verify the operation of the HSSI or to link the routers directly in order to build a larger node.
Figure 1-6 Null Modem Cable Connectors
H5692
The null modem cable uses the same 50-pin connectors as the HSSI cable, but uses the pinouts listed in Table 1-2. For connection and configuration instructions, refer to Chapter 7, “Cable Installation and Interface Configuration,” for information about attaching null modem cables.
Table 1-2 | HSSI Null Modem Cable Pinouts | | |
| | | | | |
Signal Name | | From Pins | Direction | To Pins | Signal Name |
| | | | |
RT (Receive Timing) | 2, 27 | —> | 9, 34 | TT (Terminal Timing) |
| | | | |
CA (DCE available) | 3, 28 | —> | 8, 33 | TA (DTE Available) |
| | | | |
RD (Receive Data) | 4, 29 | —> | 11, 36 | SD (Send Data) |
| | | | | |
LC (Loopback C) | | 5, 30 | —> | 10, 35 | LA (Loopback A) |
| | | | | |
ST (Send Timing) | | 6, 31 | —> | 6, 31 | ST (Send Timing) |
| | | | |
TA (DTE available) | 8, 33 | —> | 3, 28 | CA (DCE Available) |
| | | | |
TT (Terminal Timing) | 9, 34 | —> | 2, 27 | RT (Receive Timing) |
| | | | | |
LA (Loopback A) | | 10, 35 | —> | 5, 30 | LC (Loopback C) |
| | | | | |
SD (Send Data) | | 11, 36 | —> | 4, 29 | RD (Receive Data) |
| | | | | |
GND (Ground) | | 1, 26, | | 1, 26, | GND (Ground) |
| | 7, 32, | | 7, 32, | |
| | 13, 38, | | 13, 38, | |
| | 19, 44, | | 19, 44, | |
| | 25, 50 | | 25, 50 | |
| | | | | |
Loopback (not | | 12, 37 | | | |
connected) | | | | | |
| | | | | |
| | | | 12, 37 | Loopback (not connected) |
| | | | |
Not used | | 14–18, 20–24, | | 14–18, 20–24, Not used |
| | 39–43, 45–49 | | 39–43, 45–49 |
| | | | | |
Caution Although the HSSI connector and the HSSI cable are similar to SCSI-II format, they are not identical. The HSSI cable specification is more restrictive than that for the SCSI-II. If a SCSI-II cable is used instead of an HSSI cable, proper operation cannot be guaranteed.
