Specifications

4
Telephone Interface
This chapter describes the telephone line interface (TLI) that DECvoice
uses to connect to the telephone network. The chapter is divided into
two main sections: subscriber line datalink (SLD) interface and North
American TLI interface.
4.1 SLD Interface
DECvoice uses a modified version of the Intel SLD protocol to control
communication with the telephone network. The Intel SLD is a three-
wire interface for synchronous data transfer between a master and a
slave device. The master device is the controlling device. The master
controls the rate and direction of data movement by sending clock and
directional signals to the slave device. The SLD protocol supports four
full-duplex, time-multiplexed, 64 Kbits/s channels. Each channel transfers
a byte of data every 125 microseconds.
The three lines of the SLD interface are
• SCL (data clock signal),
• SDIR (data direction signal),
• SLD (data lead).
The data clock and direction signals can be common to all slave devices
connected to the master device.
SCL
The SCL clock signal controls the rate of data transfer over the SLD line.
The clock supports a rate of 512 Kbits/s.
55