APPENDIX A
TM OPTION 07A
RS-232 INTERFACE ASSEMBLY
21034-1
1.0 INTRODUCTION
This plug-in module is designed in accordance with EIA RS-232C specification and is used to
provide an electrical interface between the TymMachine 7000 (TM7000) and the RS-232 serial
interface. This document provides the user with information to configure this plug-in module.
1.1 GENERAL
DESCRIPTION
This module can be divided into two sections: Time extraction and RS-232 communication. The
RS-232 communication portion will be the main focus of this document. The time extraction
portion of this module is invisible to the user. The time is updated in this module every millisecond
unless the module is sending a time message. It is suggested that the user read this document in its
entirety for a better understanding of the options provided and what they mean.
1.2 TERMINAL
TYPE
There are two basic configurations that need to be described before serial communication can be
discussed: Data Communication Equipment (DCE) and Data Terminal Equipment (DTE). The
major differences between the two configurations are their rules and pin assignments. DTE is
designated as the initiator of the commands. DCE is designated as the responder to the commands.
This module is capable of three different output configurations:
RS-232 DCE Configuration (see Figure One)
RS-232 DTE Configuration (see Figure Two)
RS-422 DCE Configuration (see Figure Three)
Notice that the following groups of signals are switched between DTE and DCE configurations:
Read Data (RXC)
Transmit Data (TXD)
Character to Send (CTS)
Ready to Send (RTS)
Data Terminal Ready (DTR)
Data Source Ready (DSR)
It is important to remember that most computer RS-232 communication ports are set up in the DTE
configuration, which would require that this module be configured as DCE. The module can be set
to either DTE or DCE configuration by moving box pin jumpers on connector J3. The DCE
configuration is selected when the box pin jumpers are across columns A and B. The DTE
configuration is selected when the box pin jumpers are across columns B and C. This provides the
user the option of using an existing cable that has its pins switched (also known as a “null modem”
cable) or a cable that is pin-to-pin.
A-14
TM7000 TymMachine TCG/T (Rev D)
Symmetricom, Inc.