Specifications

Programming Guide 1-73

ESG Family Signal Generators Preparing for Use

Advanced Programming Information

This section provides advanced programming information for applications requiring

special techniques.

Sending BREAK Messages

A BREAK is a special character transmission that usually indicates a change in operating

conditions. Interpretation of break messages varies with the application. To send a break

message, send a non-zero value to Control Register 1 as follows (Sc is the interface select

code):

Using the Modem Control Register

Control Register 5 controls various functions related to modem operation. Bits 0 through 3

control modem lines, and bit 4 enables a self-test loopback configuration.

Modem Handshake Lines (RTS and DTR)

The Request To Send and the Data Terminal Ready lines are set or cleared at the

beginning and end of each OUTPUT or ENTER operation. In some cases, it may be

advantageous or necessary to maintain either or both in an active state. This is done by

setting bit 1 or 0 respectively in Control Register 5 as follows:

When RTS or DTR are set by Control Register 5, they are not toggled during OUTPUT or

ENTER operations, but remain constantly in an active state until the CONTROL register

is cleared by:

• writing a different value to CONTROL register 5.

• an interface reset to CONTROL register 0.

• an interface reset (Reset) from the keyboard (Shift Break on an ITF keyboard, or SHIFT

PAUSE on a 98203 keyboard).

CONTROL Sc,1;1 ! Send a Break to peripheral.

CONTROL Sc,5;2 ! Set RTS line only and hold active.

CONTROL Sc,5;1 ! Set DTR line only and hold active.

CONTROL Sc,5;3 ! Set DTR line only and hold active.

CONTROL Sc,5;0 ! Set both RTS and DTR lines active.