PC87413 datasheet(225/257 Pages) NSC

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10.0 Legacy Functional Blocks (Continued)

Revision 1.2

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10.3 SERIAL PORTS (SP1 AND SP2)

10.3.1

General Description

The identical Serial Port functional blocks SP1 and SP2 both support serial data communication with a remote peripheral

device or modem using a wired interface. The Serial Ports can function in one of three modes:

16450-Compatible mode (Standard 16450)

16550-Compatible mode (Standard 16550)

Extended mode

Extended mode provides advanced functionality for the UART.

The Serial Ports provide receive and transmit channels that can operate concurrently in full-duplex mode. They perform all

functions required to conduct parallel data interchange with the system and composite serial data exchange with the external

data channel, including:

Format conversion between the internal parallel data format and the external programmable composite serial format

Serial data timing generation and recognition

Parallel data interchange with the system using a choice of bidirectional data transfer mechanisms

Status monitoring for all phases of communication activity

Complete MODEM-control capability.

Existing 16550-based legacy software is completely and transparently supported. Module organization and specific fallback

mechanisms switch the module to 16550-Compatible mode on reset or when initialized by 16550 software.

10.3.2

Four register banks, each containing eight registers, control Serial Port operation. All registers use the same 8-byte address

space to indicate offsets 00h through 07h. The active bank must be selected by the software.

The register bank organization enables access to the banks as required for activation of all module modes, while maintaining

transparent compatibility with 16450 or 16550 software.

The Bank Selection register (BSR) selects the active bank and is common to all banks as shown in Figure 52. Therefore,

each bank defines seven new registers.

The default bank selection after system reset is 0.

Figure 52. Register Bank Architecture

BANK 0

BANK 1

BANK 2

BANK 3

Offset 07h

Offset 06h

Offset 05h

Offset 04h

LCR/BSR

Offset 02h

Offset 01h

Offset 00h

Common

Throughout

All Banks

16550 Banks

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