cx20493-35/app Conexant Systems, Inc., cx20493-35/app Datasheet - Page 79

• Manufacturer Part Number: cx20493-35/app
• Description: With Cx20493 Smartdaa?
• Manufacturer: Conexant Systems, Inc.

5.
5.1
102247B
CX81801-7x/8x SmartV.XX Modem in 128-Pin LQFP with CX20493 in 32-Pin LQFP Data Sheet
Parallel Host Interface
Overview
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.
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.
Conexant
5-1