Cirrus Logic CS61584A - Manual (Page 22)

CS61584A
22 DS261PP5
DS261PP5
response to a Loss of Signal condition for either
channel is activated by setting bit 1 of the channel
1 Mask register to 1.
8.8 Local Loopback
Selecting LLOOP causes the TCLK, TPOS, and
TNEG (or TDATA) inputs to be looped back
through the jitter attenuator (if enabled) to the
RCLK, RPOS, and RNEG (or RDATA) outputs.
The receive line interface is ignored, but data at
TPOS and TNEG (or TDATA) continues to be
transmitted to the line interface at TTIP and
TRING. During Hardware mode operation, simul-
taneous local loopback 2 of both channels is select-
ed by setting the LLOOP pin high. During Host
mode operation, local loopback 1 on a per channel
basis is controlled using the LLOOP1 bit in the
Control B registers.
During Hardware mode operation, a per channel lo-
cal loopback 1 is performed when both the RLOOP
and TAOS pins are high. The data at TPOS and
TNEG is overridden with an all-ones pattern (TAOS)
and the receive input at RTIP and RRING is ignored.
During Host mode operation, local loopback 2 can
also be selected using the LLOOP2 bit in the Control
B registers. Selecting LLOOP2 causes the TCLK,
TPOS, and TNEG (or TDATA) inputs to be looped
back to the RCLK, RPOS, and RNEG (or RDATA)
outputs. The line driver, line receiver, and jitter at-
tenuator (if enabled) are also included. The receive
line interface is ignored, but data at TPOS and
TNEG (or TDATA) continues to be transmitted to
the line interface at TTIP and TRING.
A TAOS request overrides the data transmitted to
the line interface during both local loopbacks. A
TAOS request also overrides the data received at
RPOS and RNEG (or RDATA) during local loop-
back 2. Note that simultaneous selection of local
and remote loopback modes is not valid.
8.9 Remote Loopback
During Hardware mode operation, remote loop-
backs of either channel is selected by setting the
RLOOP pin high. During Host mode operation, re-
mote loopback of each channel is controlled using
the RLOOP bit in the Control B registers.
Selecting RLOOP causes the data received from
the line interface at RTIP and RRING to be looped
back through the jitter attenuator (if enabled) and
retransmitted on TTIP and TRING. Data input to
TPOS and TNEG (or TDATA) is ignored, but data
recovered from RTIP and RRING continues to be
output on RPOS and RNEG (or RDATA).
Remote loopback is functional if TCLK is absent.
A TAOS request overrides the data transmitted to
the line interface during a remote loopback. Note
that simultaneous selection of local and remote
loopback modes is not valid.
8.10 Driver Tristate
The drivers may be independently tristated in all
modes of operation. During Hardware mode opera-
tion, setting the CON[3:0] pins of a channel to
"111X" will tristate the driver. During Host mode se-
rial port operation, the ZTX1 and ZTX2 pins perform
the driver tristate function and setting the CON[3:0]
bits in the Control B registers to "111X" will also
tristate the driver. During Host mode parallel port op-
eration, setting the CON[3:0] bits in the Control B
register to "111X" tristates the driver. In host mode,
the CS61584A powers up with CON[3:0] set to
1110, which tristates the transmitter.
8.11 Power Down
During Hardware mode operation, channel power
down is selected by setting the PD1 or PD2 pin
high. During Host mode operation, channel power
down is controlled using the PD bit in the Control
A registers. Power down places the transmitter, re-
ceiver, and jitter attenuator in reset. The RCLK,
RPOS, RNEG, RDATA, AIS, BPV, TTIP, and
TRING output pins are placed in a high-impedance
CS61584A
22 DS261F1