RC56D, RC336D, and RC144D Modem Device Sets Designer’s Guide
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Conexant
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Table 3-5. MCU Pin Signal Definitions (Cont'd)
Label
I/O Type
Signal Name/Description
TELEPHONE LINE INTERFACE
~RLY1 (~OH)
(PE0)
Ot6
Relay 1 Control (~OH). The active low ~RLY1 output can be used to control the normally open off-hook
relay. The ~PULSE function is also provided on this line in addition to the ~OH function for single
~OH/~PULSE relay application.
~RLY2 (~VOICE)
(PE1)
Ot1.6
Relay 2 Control (~VOICE). The active low ~RLY2 output can be used to control the normally open voice
relay. In voice mode, the modem asserts the this output to switch the handset from the telephone line to
a current source to power the handset so it can be used as a microphone and speaker interface to the
modem. This relay output is used in conjunction with the ~OH relay output to configure the telephone
line/telephone/audio interface circuit.
~RLY3 (~MUTE)
(PE2)
Ot1.6
Relay 3 Control (~MUTE). In W-class, the active low ~RLY3 output can be used to control the normally
open mute relay.
~RLY4 (~CALLID)
(PE3)
Ot1.6
Relay 4 Control (~CALLID). The active low ~RLY4 output can be used to control a normally open Call
ID relay if a Caller ID relay is required.
RINGD (PA0)
It
Ring Frequency. A rising edge on the RINGD input initiates an internal ring frequency measurement.
The RINGD input from an external ring detect circuit is monitored to determine when to wake up from
sleep or stop mode. The RINGD input is typically connected to the output of an optoisolator or
equivalent. The idle state (no ringing) output of the ring detect circuit should be low.
LCS (PE4)
It
Loop Current Sense. LCS is an active high input that indicates a handset off-hook status.
~EXTOH (PE4)
It
Extension Off-Hook. Active low input used to indicate the telephone line is in use by the local handset
or an extension phone.
PARALLEL HOST INTERFACE (PARALLEL HOST INTERFACE CONFIGURATION)
The parallel interface emulates a 16550A UART-compatible interface.
HA0-HA2
(PD0-PD2)
It
Host Bus Address Lines 0-2. During a host read or write operation with ~HCS low, HA0-HA2 select an
internal MCU 16550A-compatible register.
HD0-HD7
(PC0-PC7)
It/Ot6
Host Bus Data Lines 0-7. HD0-HD7 are comprised of eight three-state input/output lines providing
bidirectional communication between the host and the MCU. Data, control words, and status information
are transferred over HD0-HD7. Connect to host bus through 180
Ω
.
~HCS (PD4)
It
Host Bus Chip Select. ~HCS input low enables the MCU host bus interface.
~HWT (PD5)
It
Host Bus Read. ~HRD is an active low, read control input. When ~HCS is low, ~HRD low allows the
host to read status information or data from a selected MCU register. Connect to host bus through
180
Ω
.
~HRD (PD6)
It
Host Bus Write. ~HWT is an active low, write control input. When ~HCS is low, ~HWT low allows the
host to write data or control words into a selected MCU register. Connect to host bus through 180
Ω
.
HINT (PB7)
Ot1.6
Host Bus Interrupt. HINT output is set high when the receiver error flag, received data available,
transmitter holding register empty, or modem status interrupt is asserted. HINT is reset low upon the
appropriate interrupt service or master reset operation.
INDICATOR INTERFACE (SERIAL DTE INTERFACE CONFIGURATION)
~AAIND (PC4)
Ot6
Auto Answer Indicator. ~AAIND output ON (low) corresponds to the indicator on. ~AAIND output is
active when the modem is configured to answer the ring automatically (ATSO command • 0).
~TMIND (PB7)
Ot1.6
Test Mode Indicator. ~TMIND output ON (low) corresponds to the indicator on. ~TMIND output pulses
(indicator flashes) when the modem is in test mode and if an error is detected.
~DTRIND (PD0)
Ot1.6
DTR Indicator. ~DTRIND output ON (low) corresponds to the indicator on. The ~DTRIND state reflects
the ~DTR output state except when the &D0 command is active, in which case ~DTRIND is low.
Содержание RC144D
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