CS4239 datasheet(16/98 Pages) CIRRUS

16 / 98 page

PLUG AND PLAY

The Plug-and-Play (PnP) interface logic is com-

patible with the Intel/Microsoft Plug-and-Play

specification, version 1.0a, for an ISA-bus de-

vice. Since the part is an ISA-bus device, it only

supports ISA-compatible IRQs and DMA chan-

nels. Plug and Play compatibility allows the PC

to automatically configure the part into the sys-

tem upon power up. Plug and Play capability

optimally resolves conflicts between Plug and

Play and non-Plug and Play devices within the

system. Alternatively, the PnP feature can be by-

passed. See the Bypassing PnP section for more

information. For a detailed Plug-and-Play proto-

col description, please refer to the Plug and Play

ISA Specification.

To support Plug-and-Play in ISA systems that do

not have a PnP BIOS or a PnP-aware operating

system, the Configuration Manager (CM) TSR

and an ISA Configuration Utility (ICU) from In-

tel Corp. are used to provide these functions.

The CM isolates the cards, assigns Card Select

Numbers, reads PnP card resource requirements,

and allocates resources to the cards based on

system resource availability. The ICU is used to

keep the BIOS and the CM informed of the cur-

rent system configuration. It also aids users in

determining configurations for non-PnP ISA

cards. A more thorough discussion of the Con-

figuration Manager and the ISA Configuration

Utility can be found in the Product Development

Information document of the Plug and Play Kit

by Intel Corp. In a PnP BIOS system, the BIOS

is responsible for configuring all system board

PnP devices. Some systems require additional

software to aid the BIOS in configuring PnP ISA

cards. The PnP BIOS can execute all PnP func-

tions independently of the type of operating

system. However, if a PnP aware operating sys-

tem is present, the PnP responsibilities are shared

between the BIOS and the operating system. For

more information regarding PnP BIOS, please

refer to the latest revision of the Plug and Play

BIOS Specification published by Compaq Com-

puter, Phoenix Technologies, and Intel.

The Plug and Play configuration sequence maps

the various functional blocks of the part (logical

devices) into the host system address space and

configures both the DMA and interrupt channels.

The host has access to the part via three 8-bit

auto-configuration ports: Address port (0279h),

Write Data port (0A79h), and relocatable Read

Data port (020Bh - 03FFh). The read data port is

relocated automatically by PnP software when a

conflict occurs. Note that the Address Port can

be moved for motherboard devices. See the Ad-

dress Port Configuration section for more

details.

The configuration sequence is as follows:

1. Host sends a software key which places all

PnP cards in the sleep state (or Plug-and-

Play mode).

2. The CS4239 is isolated from the system using

an isolation sequence.

3. A unique identifier (handle) is assigned to the

part and the resource data is read.

4. After all cards’ resource requirements are de-

termined, the host uses the handle to assign

conflict-free resources

5. After the configuration registers have been

programmed, each configured logical device

is activated.

6. The part is then removed from Plug-and-Play

mode.

Upon power-up, the chip is inactive and must be

enabled via software. The CS4239 monitors

writes to the Address Port . If the host sends a

PnP initiation key, consisting of a series of 32

predefined byte writes, the hardware will detect

DS253PP2

CS4239

CrystalClear Portable ISA Audio System

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