PDSP16256/A
Signal
Description
DA15:0
DB15:0
16-bit data input bus to Network A.
Delayed data output bus in the single filter mode. Connected to the data input bus of the next device in a
cascaded chain. Input to Network B in the dual filter modes.
X31:0
Expansion input bus in the single filter mode. Connected to the previous filter output in a cascaded chain.
The inputs are not used on a single device system or on the Termination device in a cascaded chain. The
X bus provides the output from Network B in both dual modes.
F31:0
FEN
In single filter mode this bus holds the main device output. In dual mode it holds the output from Network A.
Filterenable.ThefirsthighpresentonanSCLKrisingedgedefinesthefirstdatasample.Thecontrolregister
and coefficient memory must be configured befor FEN is enabled.The signal must stay active whilst valid
data is being received and must be low if FRUN is high.
DFEN
SWAP
Delayed filter enable. This output is connected to the Filter Enable input of the next device in a cascaded
chain when moving towards the termination device and with multiple stand-alone EPROM-loaded
configurations. It is used to coordinate the control logic within each device.
Selects either the upper or lower set of coefficients for Bank Swap. A low selects the lower bank, a high the
upper bank.
FRUN
DCLR
In EPROM load mode, when high this signal allows continuous filter operations to occur without the need for
the initial FEN edge. If the device is not a single, interface or master device then this pin must be tied low.
A low on this signal on the SCLK rising edge will clear all the internal accumulators.
need only remain
DCLR
low for a single cycle, signal BUSY will indicate when the internal clearing is complete. After a clear the
device must be re-synchronised to the data stream using FEN. It is recommended that FEN is taken low
at the same time as clear. FEN may then be taken high to synchronise the data stream once BUSY has
returned low.
C15:0
A7:0
16-bit coefficient input bus. In the Byte mode of operation, C15:8 have alternative uses as explained in the
text.
Coefficient address bus. In the EPROM mode A7:0 are address outputs for an EPROM. In the remote host
mode they are inputs from the host. A7 is not used when coefficients are loaded as 16-bit words.
CCS
WEN
This pin is similar in operation to A7:0 and provides a higher order address bit. When low the coefficients
are loaded, when high the control register is loaded.
In the remote mode this pin is an input which when low enables the load operation. In the EPROM mode
it is an output which provides the write enable for other slave devices.
CS
This pin is always an input and must also be low for the internal write operation to occur.
BYTE
When this pin is tied low, coefficients are loaded as two 8-bit bytes. When the pin is high they are loaded
as 16-bit words. In the EPROM mode this pin is ignored.
EPROM
When this pin is tied low coefficients are loaded as bytes from an external EPROM. The device outputs an
address on A7:0. When the pin is high coefficients must be loaded from a remote master. They can then
be transferred individually rather than as a complete set.
SCLK
The main system clock; all operations are synchronous with this clock. The clock rate must be either 1, 2,
4, or 8 times the required data sampling rate. The factor used depends on the required filter length.
CLKOP
OEN
This output, when used to enable SCLK, can provide a data sampling clock. It has the effect of dividing the
SCLK rate by 1, 2, 4 or 8 depending on the filter mode selected.
OEN
Tri-state enable for the F bus. When high the outputs will be high impedance.
device and does not therefore take effect until the first SCLK rising edge
is registered onto the
BUSY
RES
A high on this signal indicates that the device is completing internal operations and is not yet able to accept
new data. The signal is used during automatic EPROM loading, reset and accumulator clearing.
When this pin is low the control logic and accumulators are reset. In the EPROM mode it will initiate a load
sequence when it goes high.
NOTES
1. Unused buses (e.g. X31:0 when the device is configured in single or termination mode) can be set to any value. They should however be
maintained at a valid logic level to avoid an increase in power consumption.
2. To ensure correct input voltage thresholds are maintained all the VDD and GND pins must be connected to adequate power and ground planes.
Table 1 Pin descriptions
3
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