Tadpole SPARCbook 3 series, Reference Manual

Page: 120 / 216

9-2
MODEM
Internal Modem Overview
9.1 Internal Modem Overview
The MCU provides the interface between the host system and DPL. It
incorporates a processor core and a 16C450 UART-type parallel interface,
and supports an enhanced AT command set as well as Fax Class 2
commands.
The MDP supports data and facsimile communications. As a data modem,
it operates at up to 14400 bps (V32.bis), and with data compression (V42)
can increase this by a factor of four. As a fax modem it supports V29, V27
ter and V21 channel 2 recommendations.
The modem data pump interfaces to the telephone line via a data access
arrangement (DAA) which provides the required line isolation and
impedance matching.
Note
The DAA is only approved for connection to public telephone systems in the U.S.A.
and Canada.
The EPROM provides storage for the MCU’s operational software, and the
SRAM provides storage for parameters and the S-registers.
The modem interface can be controlled using Hayes compatible commands
written to the parallel interface of the MCU. Commands are sent to the
interface using character strings, and these are interpreted by the MCU and
acted on appropriately.
Command characters and data for transmission onto the telephone line are
written into the MCU’s transmit buffer. Data received from the telephone
line and status information from the DPL can be read from the MCU’s
receive buffer.
The modem interface operates in two modes: Command Mode or On-Line
Mode. In Command Mode, characters written to the transmit buffer are
regarded as being command characters. In the On-line mode, data written
to this location (apart from the escape se++) are transmitted onto
the telephone line.
9.2 Interface Control
The SPARCbook implementation of Solaris provides the user with
complete control of the modem via a graphical user interface. Behind this
interface, the host controls the modem via a set of registers which are part
of the parallel interface of the MCU.
S3GX_TRMBook Page 2 Friday, September 19, 1997 11:39 am