CX81801 查看數據表（PDF） - Conexant Systems

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CX81801

V.92/V.34/V.32bis Modem in 128-Pin TQFP with CX20493 SmartDAA® and Optional CX20442 Voice Codec

Conexant Systems 

CX81801-7x/8x SmartV.XX Modem Data Sheet

5.

Parallel Host Interface

The modem supports a 16550A interface in parallel interface versions. The 16550A

interface can operate in FIFO mode or non-FIFO mode. Non-FIFO mode is the same as

16450 interface operation. FIFO mode unique operations are identified.

5.1

Overview

The parallel interface registers and the corresponding bit assignments are shown in

Table 5-1.

The modem emulates the 16450/16550A interface and includes both a 16-byte receiver

data first-in first-out buffer (RX FIFO) and a 16-byte transmit data first-in first-out buffer

(TX FIFO). When FIFO mode is selected in the FIFO Control Register (FCR0 = 1), both

FIFOs are operative. Furthermore, when FIFO mode is selected, DMA operation of the

FIFO can also be selected (FCR3 = 1). When FIFO mode is not selected, operation is

restricted to 16450 interface operation.

The received data is read by the host from the Receiver Buffer (RX Buffer). The RX

Buffer corresponds to the Receiver Buffer Register in a 16550A device. In FIFO mode,

the RX FIFO operates transparently behind the RX Buffer. Interface operation is

described with reference to the RX Buffer in both FIFO and non-FIFO modes.

The transmit data is loaded by the host into the Transmit Buffer (TX Buffer). The TX

Buffer corresponds to the Transmit Holding Register in a 16550A device. In FIFO mode,

the TX FIFO operates transparently behind the TX Buffer. Interface operation is

described with reference to the TX Buffer in both FIFO and non-FIFO modes.

102199B

Conexant

5-1

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