as3588a austriamicrosystems, as3588a Datasheet - Page 4

• Manufacturer Part Number: as3588a
• Description: Digital Time/space Crosspoint Switch
• Manufacturer: austriamicrosystems

Data Sheet
quential addressing information. The count difference
between the bases is 32 which is two time slots, the
minimum PCM propagation time. The device activates
the output channels one bit time before input channels
are strobed. This feature allows inputs and outputs to
be tied together cancelling any analogue delay of
digital outputs up to a time which is specified in the
timing diagramme.
Serial Input PCM Conversion
Serial data at 2048 kbit/sec is received at the eight
PCM inputs INP PCM1 to INP PCM7. Each serial port
accepts 32 64 kbit channels of data, each channel
containing an 8-bit word which may represent a PCM-
encoded analogue/voice sample as provided by a
codec (e.g. AMS` S44231 to S44238 or AS3554 to
AS3569 codec family). This serial input word is con-
verted into parallel data by a serial to parallel PCM
converter.
Data Memory and Connection Memory
The parallel data is stored in the 256 x 8 Data Memory
which is updated every frame period. The locations in
the Data Memory are associated with particular chan-
nels in particular PCM input ports. The locations in the
256 x 9 Connection Memory are associated with par-
ticular PCM output streams. These locations can be
accessed by the microprocessor which controls the
device. When a channel is due to be transmitted on a
PCM output stream the data can either be switched
from a PCM input channel in space (INP PCM1 to
INP PCM7)) or time (slot 1 to 32). In this case the 9 th
bit in the control memory is set to "0". Alternatively it
can originate from the Connection Memory. In this
case the 9 th bit of the control memory is set to "1". If
the data is switched from an input, the contents of the
Connection Memory associated with the output chan-
nel is used to point to the Data Memory locations. This
Data Memory address corresponds to the channel of
the PCM input stream on which the data for switching
has arrived. If the data for the output channel
originates from the microprocessor then the contents
of the Connection Memory associated with the PCM
output Channel are output directly and this data is
output as message constantly once every frame until
the microprocessor intervenes.
Serial Output PCM Conversion
The parallel channel data is converted back into a se-
rial PCM stream by a parallel to serial PCM converter
and is transmitted at the eight PCM output ports OUT
PCM1 to OUT PCM7.
Microprocessor Interface
The asynchronous microprocessor interface is con-
trolled by 9 control signals (WR, RD, CS1, CS2, A1,
S1, A2, S2, DR) and provides data and instruction
transfer via the 8-bit data bus (D7 to D0). For each of
Rev. 3.1
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the six available operations two to four data bytes and
one instruction byte are written into a five level deep
stack. After a check of the correctness the function is
executed. Data bytes are defined by a low level on the
C/D input while a command byte is defined by a high
level. The active high Data Ready output pin of
AS3588
microprocessor when transfer information is ready.
During long instructions like an initialization routine
after RESET or execution of instruction 6 only valid
opcodes with the associated datafield are accepted;
the execution of the new instruction is started after the
current instruction has been completed. Memory con-
tent and status information can be extracted by read-
ing the two internal registers OR1 and OR2 and using
C/D as multiplexing control signal. OR1 is selected by
a low level on the C/D input and contains either data
from the data memory or the connection memory.
OR2 is selected with a high level and contains the op-
code and additional status information. Read opera-
tions are only executed if the device is fully selected
with CS1=CS2=0 and A1=S1 and A2=S2. There are
no restrictions on the sequence of read and write op-
erations as long as only one of the control pins (RD,
WR) is selected. If both pins are pulled low, the inter-
face bus goes into high impedance state. The register
contents is maintained as long as this condition per-
sists and is updated 3 cycles after a new opode or an
OR2 read. Single or multiple read operations of OR1
and OR2 should be carried out with separate read
strobes which are responsible of stepping through the
instruction flow.
Software Control
AS3588A performs two switching functions and four
auxiliary functions for diagnostic purposes and data in-
sertion from the microprocessor interface.
1) PCM CHANNEL CONNECTION
This function connects a PCM input channel to a PCM
output channel. The control information from the
microprocessor consists of four data bytes and one
command byte. Byte one and two contain information
about the PCM input line and PCM input channel that
is written into the connection memory. Byte three and
four contain information on the PCM output line and
the PCM output channel and act as address to the
specific connection memory location. If AS3588 is se-
lected by CS1=CS2=0 and if the condition A1=S1 and
A2=S2 is met, the command instruction is executed as
defined. If the device is selected by CS1 and CS2 only
this command will perform a disconnect function on
the specific output channel. If the instruction code was
found to be invalid, DR is driven low until a valid
instruction code is supplied; the registers are not
modified.
2) PCM CHANNEL DISCONNECTION
This function disconnects a PCM output channel. The
control information from the microprocessor consists
provides
a
handshake
signal
AS3588A
July 1999
to
the