FDC37B727-NS Standard Microsystems (SMSC), FDC37B727-NS Datasheet - Page 120

• Manufacturer Part Number: FDC37B727-NS
• Manufacturer: Standard Microsystems (SMSC)

Specifications of FDC37B727-NS

• Pin Count: 128
• Lead Free Status / RoHS Status: Compliant

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.
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
This function allows data
nROMCS
These alternate functions
H
L
L
nROMOE
BIOS BUFFER
H
X
L
120
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
RD[0:7] data to SD[0:7] bus
SD[0:7] data to RD[0:7]
Isolation
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.
DESCRIPTION
and
isolate
the
buses.