Specifications

Telephone Interface 57
4.1.1 SLD System
In an Intel SLD master-slave system, the master controls the rate and
direction of data flow by generating clock and directional signals. The
slave reads the clock and direction signals.
In the DECvoice system, the TLI assembly serves as the master and the
DTC04 module as the slave. The TLI controls the rate and direction of
data transfer between the telephone network and the module.
NOTE
Although the module is the slave device in a timing sense, it is
the master device in a logical sense. The module provides the
programming information to any interface device connected to
it. The module also provides the intelligence to run telephone
transactions.
4.1.2 DECvoice Modifications to the Intel SLD Interface
The SLD protocol is designed for systems where the master and slave
devices (chips) are on the same printed circuit board. In the DECvoice
system, the master and slave devices are on separate boards. The SLD
protocol has been modified in three ways to accommodate this separation.
• The SLD data lead wire has been split into two unidirectional wires.
• The telephone line interface sends an additional byte of identification
data to the DTC04 module.
• A reset line has been added so the module can send a reset signal to
the TLI assembly.
4.1.2.1 SLD Data Lead
The SLD protocol was designed for use on a single board. When the SLD
master and slave devices are on one board, time delays are short for data
travel. On a single board, the SLD data lead can handle bidirectional
data travel with a minimal amount of time delay between the master and
slave devices.
In the DECvoice system, the master and slave devices are on separate
boards. Data must travel over a cable from the DTC04 module (slave) to
the TLI (master). The SLD data can be separated into two unidirectional
signals.