TNETA1585 Datasheet, PDF (11/32 Pages) Texas Instruments – ATM TRAFFIC MANAGEMENT SCHEDULER DEVICE WITH RECEIVE UTOPIA AND COPROCESSOR INTERFACES

TNETA1585
ATM TRAFFIC MANAGEMENT SCHEDULER DEVICE
WITH RECEIVE UTOPIA AND COPROCESSOR INTERFACES
SDNS041A – NOVEMBER 1996 – REVISED JULY 1998
RM-cell-contents FIFO D
When the TNETA1575 reads the next-cell register and an indication is given that an RM cell should be sent from
the RM-cell contents FIFO D, the TNETA1575 must make 12 accesses to control-memory location 10004h to
fetch one entire cell payload. The data that is returned by the TNETA1585 is in big-endian format as follows:
Byte 0 (31–24)
Byte 1 (23–16)
Byte 2 (15–8)
Byte 3 (7–0)
The ordering and formatting of data (as it is sequentially read from this register) is:
Word 0 – Bytes 0, 1, 2, 3
Word 1 – Bytes 0, 1, 2, 3
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coprocessor interface
The coprocessor interface consists of a group of unidirectional serial channels through which real-time
information concerning the transmission and reception of cells by the SAR/switch port is passed between the
TNETA1585 and the SAR/switch port. Reset and interrupt capabilities also are provided by the coprocessor
interface. The unidirectional serial-interface implementation by the TNETA1575 SAR is described below.
Similar requirements apply when interfacing to a different SAR device or a switch port. The coprocessor
interface consists of:
Received cell-indication interface (RCCX)
Transmitted cell-indication interface (TCCX)
Data-availability interface (DAX)
COP full-indication interface (COPFULL)
received-cell-indication interface (RCCX)
A serial-bit interface allows the TNETA1575 to signal to the TNETA1585 that a cell has been received on the
UTOPIA interface on a particular channel. This interface is necessary to avoid duplicating the hardware that
is used to resolve a virtual path identifier (VPI) or virtual channel identifier (VCI) to a channel number. When a
cell is received, the VPI/VCI value from the header is extracted by the TNETA1575 and is used as a key in a
lookup algorithm to resolve its associated channel number. When the lookup is complete, the TNETA1575
passes relevant information to the TNETA1585 by sending a 13-bit frame formatted as follows:
Channel number (12–2)
Good/bad cell indicator (1)
Framing (0)
Bits 12–2 (channel number). These bits indicate on which of the 2K channels the last cell was received.
Bit 1 (good/bad cell indicator). This bit indicates whether or not the last cell passed the lookup test or if it should
be discarded. The bit is encoded as follows:
BIT 1
0
1
INDICATION
Cell is good (VPI/VCI was found in the lookup)
Cell should be discarded
Bit 0 (framing). This bit is set to a 1 to denote the start of a frame.
The frame is transmitted to the TNETA1585 through the RCCX terminal starting with bit 0. When a frame is not
actively being transmitted, the RCCX terminal is driven to a 0.
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