FDC37B78X View Datasheet(PDF) - SMSC -> Microchip

Part Name

Description

Manufacturer

FDC37B78X

Enhanced Super I/O Controller with ACPI Support, Real Time Clock and Consumer IR

SMSC -> Microchip 

BIOS BUFFER

The chip contains one 245 type buffer that can

be used for a BIOS Buffer. If the BIOS buffer is

not used, then nROMCS must be tied high or

pulled up to Vcc with a resistor so as not to

interfere with the boot ROM. This function

allows data transmission from the RD bus to the

SD bus or from the SD bus to the RD bus. The

direction of the transfer is controlled by

nROMOE. The enable input, nROMCS, can be

used to disable the transfer and isolate the

buses.

nROMCS

L

L

H

nROMOE

L

H

X

DESCRIPTION

RD[0:7] data to SD[0:7] bus

SD[0:7] data to RD[0:7]

Isolation

RD Bus Functionality

The following cases described below illustrate

the use of the RD Bus.

Case 1: nROMCS and nROMOE as original

function. The RD bus can be used as the RD

bus or one or more RD pins can be

programmed as alternate function. These

alternate functions behave as follows: if in RD to

SD mode, any value on RDx will appear on SDx;

if in SD to RD mode, SDx will not appear on

RDx, RDx gets the alternate function value.

Note: In this case, nROMCS=0, nROMOE=1.

RD bus is disabled, and nothing appears on the

SD bus. Note: any RD bus pin can be

programmed as an alternate function, however,

if nROMCS=0, then anything on the RD bus will

appear on the SD bus.

Case 3: nROMCS as GPIO function. (nROMCS

internally tied to VDD.) The RD bus

floats - cannot use as a bus. Any pin can be

programmed as an alternate function.

Case 4: nROMCS and nROMOE as GPIO

function. Same as Case 3.

Case 2: nROMOE as GPIO function. (nROMOE

internally tied to ground). In this case, the RD

bus is a unidirectional bus (read only) controlled

by nROMCS. If nROMCS = 0, the values on

RD0-7 appear on SD0-7. If nROMCS = 1, the

Case 5: Parallel IRQ enabled; RD Bus pins,

nROMOE, nROMCS are used as IRQ pins.

122

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