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Circuit Description
System memory consists of 64kB ROM and 32kB RAM. Ail of RAM is backed up. ROM and RAM are
selected by chip select lines, and data is accessed by the units position of the byte.
These circuits control signal transmission between the internal MODEM and the LIU or a remote MODEM.
The R96DFXL MODEM is a single-chip fax-MODEM having features to detect and generate DTMF tones.
TX OUT is the MODEM output port, and RX IN is the input port. /PORI is the IFC signal which enables
MODEM initialisation at system power on. DO - D7 are data buses. RSO- RS4 are internal register select
signals which determine the mode. /MCS is the chip select signal, /RD and /WR are the read and write
control signals. RLSD is used for v.24 interface-related signals and /MIRQ is the MODEM interrupt.
Refer to Figure 5-14 for available R96DFXL I/O ports.
CIRCUIT NAME
PIN NO PIN NAME
1
2
3
4
5
ACTIVE STATE (H)
0
HALFTONE MODE
I
0
I
I
0
RX PATH
0
I
I
I
I
I
I
DESCRIPTION
BINARY MODE
EXTERNAL TEL. IN USE
REMOTE PATH
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