4 SERIAL I/O CARDS
3021M100-002
4-15
4.4.2 Speeds Supported by the X.21 Serial I/O
The X.21 port can operate, without split clocking, at the following speeds:
• 50 bps - 2,048 Kbps for external clocking
• 375 bps - 2,048 Kbps for internal clocking
4.4.3 X.21 DTE/DCE Interface Configuration
The X.21 Serial I/O Card’s port can be configured either as a DTE or a DCE
device. The DCE/DTE strapping has been silk-screened on the I/O card to aid in
configuration.
DCE
When configured as a DCE device, the port transmits DCD, DSR and CTS and the
synchronous clock signals TXC and RXC. The port must receive DTR and RTS
from the attached DTE. Terminals, printers, controllers and hosts are always DTE
devices.
DTE
When configured as a DTE device, the port transmits DTR, RTS and ETXC and
receives DCD, DSR and CTS and the synchronous clock signals TXC and RXC
from the attached DCE.
A jumper at LK3 provides DTE/DCE configuration. The presence or absence of
the jumper determines whether the port will be DTE or DCE.
• DTE mode - jumper is off
• DCE mode - jumper is on
Figure 4-12 X.21 DTE/DCE Configuration Jumper
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