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2.0

Device Architecture and Conﬁguration

The PC8739x SuperI/O device comprises a collection of legacy and proprietary functional blocks. Each functional block is

described in a separate chapter in this document. However, some parameters in the implementation of each functional block

may vary per SuperI/O device. This chapter describes the PC8739x structure and provides all logical device specific infor-

mation, including special implementation of generic blocks, system interface and device configuration.

2.1

OVERVIEW

The PC8739x consists of 9 logical devices, the host interface, and a central set of configuration registers, all built around a

central, internal bus. The internal bus is similar to an 8-bit ISA bus protocol. See Figure 1, which illustrates the blocks and

related logic.

The system interface serves as a bridge between the external LPC interface and the internal bus. It supports 8-bit Read and

Write transactions for I/O, memory, DMA, and FWH, as defined in Intel’s

LPC Interface Speciﬁcation, Revision 1.01.

The central configuration register set is ACPI compliant and supports a PnP configuration. The configuration registers are struc-

tured as a subset of the Plug and Play Standard registers, defined in Appendix A of the

Plug and Play ISA Specification, Re-

vision 1.0a by Intel and Microsoft. All system resources assigned to the functional blocks (I/O address space, DMA channels

and IRQ lines) are configured in, and managed by, the central configuration register set. In addition, some function-specific

parameters are configurable through the configuration registers and distributed to the functional blocks through special control

signals.

2.2

CONFIGURATION STRUCTURE AND ACCESS

The configuration structure is comprised of a set of banked registers which are accessed via a pair of specialized registers.

2.2.1

The Index-Data Register Pair

Access to the SuperI/O configuration registers is via an Index-Data register pair, using only two system I/O byte locations.

The base address of this register pair is determined during reset, according to the state of the hardware strapping option on

the BADDR pin. Table 5 shows the selected base addresses as a function of BADDR.

Table 5. BADDR Strapping Options

The Index register is an 8-bit read/write register located at the selected base address (Base+0). It is used as a pointer to the

configuration register file, and holds the index of the configuration register that is currently accessible via the Data register.

Reading the Index register returns the last value written to it (or the default of 00h after reset).

The Data register is an 8-bit register (Base+1) used as a data path to any configuration register. Accessing the Data register

actually accesses the configuration register that is currently pointed to by the Index register.

BADDR

I/O Address

Index Register

Data Register

2Eh

2Fh

4Eh

4Fh

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