PC87393 datasheet(106/148 Pages) NSC

106 / 148 page

106

www.national.com

7.0

X-Bus Extension

Notes: This section applies to the PC87393 and PC87393F only.

FWH-related descriptions apply to the PC87393F only.

7.1

OVERVIEW

The PC8739x provides an X-Bus extension to the LPC bus to enable the ISA-like interface to external 8-bit peripherals. De-

code logic, described in the

Device Architecture and Configuration chapter, defines the addresses for which the X-Bus gen-

erates transactions. These transactions may be in the I/O address space and the memory address space or in the FWH

memory address space. Using the X-Bus interface, the PC8739x serves as a bridge for such transactions into the X-Bus.

Figure 21 is a schematics block diagram of the X-Bus bridging function. For details on the decoder functions, see the

Device

Architecture and Configuration chapter. All other functions are described in detail in this chapter.

Figure 21. X-Bus Block Diagram

7.2

IRQ ROUTING

The PC8739x supports up to four IRQ inputs, PIRQA through PIRQD. These pins may be used to support legacy devices

that are connected on the X-Bus. The PC8739x enables any of these interrupts to be routed to any one of fifteen host IRQs.

The IRQ inputs are mapped by X-Bus PIRQA-D Mapping registers at F8h and F9h. XIRQCA through XIRQCD registers en-

able the user to define the interrupt as active high or low, and to route it to a wake-up event.

7.3

X-BUS TRANSACTIONS

The X-Bus extension supports 8-bit I/O or memory read/write cycles.

The zone mapping of the chip select signals determines how X-Bus read and write cycles correspond to memory and I/O

bus cycles. The zone mapping to a select signal, XCS1-0, must be enabled regardless of whether the I/O device is using

the chip select signal. Signal mapping to a pin may be disabled when the select signal is not required for an off-chip interface.

LPC

Bus

X-Bus

Configuration

I/O

Address

Memory

Address

Decoder

Bus

Cycle

Generator

XCS0

XCS1

XA19-0

X-Bus Interface

Device Architecture Component

XRD XWR

XSTB2-0

XRDY

XD7-0

IRQ Router

IRQ

Serializer

PIRQ(A-D)

XCNF2-0

XIORD XIOWR

PC87393 Datasheet(PDF) 106 Page - National Semiconductor (TI)

PC87393 Datasheet(HTML) 106 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL