FDC37B787QF SMSC [SMSC Corporation], FDC37B787QF Datasheet - Page 120

• Manufacturer Part Number: FDC37B787QF
• Description: Super I/O Controller with ACPI Support, Real Time Clock and Consumer IR
• Manufacturer: SMSC [SMSC Corporation]

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.
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.
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
These alternate functions
107
appear on SD0-7. If nROMCS = 1, the 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 5: Parallel IRQ enabled; RD Bus pins,
nROMOE, nROMCS are used as IRQ pins.