Revision 1.02 – June 27, 2006
S5935 – PCI Product
Data Book
Add-On FIFO Status Indicators
Signal
RDFIFO#
WRFIFO#
FRC#
Function
The Add-On interface implements FIFO status pins to
indicate the full and empty conditions of the PCI to
Add-On and Add-On to PCI FIFOs. These may be
used by the Add-On to allow data transfers between
the FIFO and memory, a peripheral, or even a cas-
caded external FIFO. The RDEMPTY and WRFULL
status outputs are always available to the Add-On.
Additional status signals are multiplexed with the byte-
wide, non-volatile memory interface pins. If the S5935
is configured for Add-On initiated bus mastering, these
status signals also become available to the Add-On.
FIFO status is also indicated by bits in the Add-On
General Control/Status and Bus Master Control/Status
Registers. The table below lists all FIFO status outputs
and their functions.
Reads data from the PCI to Add-On FIFO
Writes data into the Add-On to PCI FIFO
Reset PCI to Add-On FIFO pointers and
1
status indicators
FWC#
AMREN
AMWEN
Reset Add-On to PCI FIFO pointers and
1
status indicators
Enable bus mastering for Add-On initiated
1
PCI reads
Enable bus mastering for Add-On initiated
1
PCI writes
1. These signals are only available when a serial non-volatile mem-
ory is used and the S5935 is configured for Add-On initiated bus
mastering.
Signal
Function
PCI Bus Mastering with the FIFO
RDEMPTY
Indicates empty condition of the PCI to
Add-On FIFO
The S5935 may initiate PCI bus cycles through the
FIFO interface. The S5935 allows blocks of data to be
transferred to and from the Add-On by specifying a
source/destination address on the PCI bus and a
transfer byte count. This DMA capability allows data to
be transferred across the PCI bus without host CPU
intervention.
WRFULL
FRF
Indicates full condition of the Add-On to
PCI FIFO
Indicates full condition of the PCI to Add-
1
On FIFO
FWE
Indicates the empty condition of the Add-
Initiating a bus master transfer requires programming
the appropriate address registers and transfer byte
counts. This can be done from either the PCI interface
or the Add-On interface. Initiating bus master transfers
from the add-on is advantageous because the host
CPU does not have to intervene for the S5935 to
become a PCI Initiator. At the end of a transfer the
S5935 may generate an interrupt to either the PCI bus
(for PCI initiated transfers) or Add-On interface (for
Add-On initiated transfers).
1
On to PCI FIFO
1. These signals are only available when a serial non-volatile mem-
ory is used and the device is configured for Add-On initiated bus
mastering.
Add-On FIFO Control Signals
The Add-On interface implements FIFO control pins to
manipulate the S5935 FIFOs. These may be used by
Add-On to control data transfer between the FIFO and
memory, a peripheral, or even a cascaded external
FIFO. The RDFIFO# and WRFIFO# inputs are always
available. These pins allow direct access to the FIFO
without generating a standard Add-On register access
using RD#, WR#, SELECT#, address pins and the
byte enables.
Add-On Initiated Bus Mastering
If bit 7 in location 45h of an external serial non-volatile
memory is zero, the Master Read Address Register
(MRAR), Master Write Address Register (MWAR),
Master Read Transfer Count (MRTC), and Master
Write Transfer Count (MWTC) are accessible only
from the Add-On interface. Add-On initiated bus mas-
tering is not possible when a byte-wide boot device is
used due to shared device pins. When configured for
Add-On initiated bus mastering, the S5935 transfers
data until the transfer count reaches zero, or it may be
configured to ignore the transfer count.
Additional control signals are multiplexed with the
byte-wide, non-volatile memory interface pins. If a
serial non-volatile memory is used and the S5935 is
configured for Add-On initiated bus mastering, these
control signals also become available. For PCI initi-
ated bus mastering, AMREN, AMWEN, FRC#, and
FWC# functionality is always available through bits in
the Bus Master Control/Status and Add-On General
Control/Status Registers. The FIFO control inputs are
listed below.
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DS1527
137
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
