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3-13
ARCHITECTURAL OVERVIEW
S5933
ADD-ON INTERFACE
The S5933 provides a simple, general-purpose inter-
face to the Add-On bus. The Add-On data path is a 32-
bit bus for the S5933. Data transfers to/from the
S5933 internal registers are accomplished through a
chip select decode in conjunction with either a read
or write strobe. The S5933 provides dedicated pins
which allow its FIFOs to be used in the implementa-
tion of custom DMA ports or additional external
FIFOs (if necessary).
The output pins on the Add-On interface include an
interrupt source, a buffered clock, and a software-
controllable reset. The interrupt output pin is provided
to signal when a selected mailbox or self-test event
occurs from the PCI interface. The buffered clock
output is a possible Add-On cost reduction feature,
and in addition provides synchronization for Pass-
Thru data transfers. The software-controllable reset
from the S5933 provides Add-On hardware with a
means for proper handling of a system’s “soft” reboot
(e.g.CTRL-ALT-DEL).
NON-VOLATILE MEMORY INTERFACE
The non-volatile interface allows customization of the
S5933 and provides for an optional BIOS ROM on
the PCI bus. The non-volatile memory can be either a
serial device or a byte-wide device. Serial devices
may range from 128 bytes through 2048 bytes, and
byte-wide devices from 128 bytes through 65,536
bytes.
As an example, the Vendor and Device ID numbers
in the PCI configuration space can be initialized to
reflect values contained in the external non-volatile
memory. After initialization, a user’s own Vendor and
Device ID is then presented by the S5933 when re-
quested by the PCI bus.
For some non-volatile devices, it is possible to write
the non-volatile memory from the PCI interface. This
feature lets the system designer establish a field up-
grade strategy for the BIOS software or a method to
support various system platforms with only one Add-
On board product.
Use of a byte-wide non-volatile memory device is
shown in Figure 6; Figure 7 shows a serial device
with the S5933.
16
EA [15:0]
ERD#
EWR#
EQ[7:0]
8
1
EPROM
64KX8
A
CS#
OE#
Q
S5933
Figure 6. Byte-Wide Non-Volatile Memory Interface
Figure 7. Serial Non-Volatile Memory Interface
SERIAL
E2 PROM
24CO2
256X8
24CO4
512X8
24CO8
1KX8
24C16
2KX8
S5933
SCL
SDA
1
R