S/UNI®-JET Data Sheet
Released
LOOPT
The LOOPT bit selects the transmit timing source. When a logic one is written to LOOPT, the
transmitter is loop-timed to the receiver. When loop timing is enabled, the receive clock
(RCLK) is used as the transmit timing source. The transmit nibble stuffing is derived from the
nibble stuffing in the receive PLCP frame (for DS3 or E3 PLCP frame transmission). The
FIXSTUFF bit must be set to logic zero if the LOOPT bit is set to logic one. When a logic
zero is written to LOOPT, the transmit clock (TICLK) is used as the transmit timing source.
The nibble stuffing is derived from the REF8KI input, or is fixed internally as determined by
the FIXSTUFF bit in the SPLT Configuration Register (for DS3 or E3 PLCP frame
transmission only). Setting the LOOPT bit disables the effect of the TICLK and TXREF bits
in the S/UNI-JET Transmit Configuration and S/UNI-JET Configuration 2 Registers
respectively, thereby forcing flow-through timing.
FRMRONLY
The FRMRONLY bit controls whether the S/UNI-JET is operating solely as a DS3, E3, or J2
framer/transmitter. If FRMRONLY is set to logic one, the PLCP, and ATM blocks are
disabled and the RDATO, REF8KO/RFPO/RMFPO, RSCLK, ROVRHD, TFPO/TMFPO,
TFPI/TMFPI, and TDATI I/O pins are enabled. The ATM interface inputs are ignored and the
outputs are tri-stated. If FRMRONLY is set to logic zero, the PLCP and ATM blocks are
enabled and the LCD, RPOH, RPOHCLK, RPOHFP, TPOH, TIOHM, and TPOHFP I/O pins
are enabled and the ATM interface inputs and outputs are enabled.
TOCTA
The TOCTA bit enables octet-alignment or nibble-alignment of the transmit cell stream to the
transmission overhead when the arbitrary transmission format is chosen (TFRM[1:0] = 11
binary and SPLT Configuration register bit EXT = 1). This bit has no effect when DS3, G.751
E3, G.832 E3, J2, T1, or E1 formats are selected since octet or nibble alignment is specified
for these formats. When the arbitrary transmission format is chosen and TOCTA is set to logic
one, the ATM cell nibbles or octets are aligned to the arbitrary transmission format overhead
boundaries (as set by the TIOHM input). Nibble alignment is chosen if the FORM[1:0] bits in
the SPLT Configuration are set to 00. Byte alignment is chosen if these FORM[1:0] bits are
set to any other value. The number of TICLK periods between transmission format overhead
bit positions must be divisible by four (for nibble alignment) or eight (for byte alignment).
When TOCTA is set to logic zero, no octet alignment is performed , and there is no restriction
on the number of TICLK periods between transmission format overhead bit positions.
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990267, Issue 3
83
PMC [ PMC-SIERRA, INC ]
