RFX144V24-S23 and RFX96V24-S23 Modem Designer’s Guide
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3.2.7 V.23 Mode Operation
The V.23 mode operates when CONF = 24h. DSP RAM Access 2 does not operate in this mode.
V.23 Mode Transmitter and Receiver
In both V.23 Full-duplex and Half-duplex operation, the transmitter is activated by RTSn (low) or RTSP = 1. CTSn (low) and
CTSP will respond as described in Table 1-1, and data may be then sent using the TXD pin (PDM = 0) or TBUFFER (PDM =
1). V.23 data received by the modem will be presented to the host at RXD (PDM = 0) or both DBUFF and RXD (PDM = 1).
During V.23 communication, the transmitter squelch (TXSQ), break send (BRKS), and Receive Compromise Equalizer
(CEQ) may be activated at any time. All other changes to the V.23 configuration (e.g., word size, parity, stop bit selection,
parallel data mode, half duplex mode) require the host to set the SETUP bit before any action is taken by the modem.
In serial mode (PDM = 0), start, stop, data length, and parity are all determined by the host during transmission, and all
received start, stop, and parity bits are presented to the host at the RXD pin.
In parallel mode (PDM = 1), start, stop, data length, and parity selection is done via the modem interface memory. During
transmission, the host need only provide data bits to the TBUFFER register, and the modem will add the requested start,
stop, and parity bits. During reception, start and stop bits are always stripped by the modem. The parity bit is NOT, in
general, stripped from the data by the modem, and remains with the data as the most significant bit, for backward
compatibility with previous Rockwell products. In parallel mode, the modem senses overrun, underrun, framing, and parity
errors.
Figure 3-5 shows how to setup various V.23 transmit and receive modes.
3.2.8 Caller ID Mode Operation
The Caller ID (V.23 Receive only) mode operates when CONF = 22h.
New Control Bits
Due to the additional capabilities of V.23 equipped modems, Caller ID mode operates slightly differently than in the
RFX96V24 and RFX96V24-S modems.
The Receive Compromise Equalizer included in V.23 mode also functions in Caller ID mode. It may be enabled at any time
during Caller ID reception by setting CEQ to a 1.
The V.23 control bits ANS (Answer) and V23HDX must be set to zero in Caller ID mode.
With these exceptions, Caller ID mode functions as described in Section 10.
Figure 3-6 shows the Caller ID setup.
Summary of Contents for RFX144V24-S23
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