Rainbow Electronics DS2180A User Manual
Page 7
DS2180A
041995 7/36
COMMON CONTROL REGISTER Figure 4
(MSB)
(LSB)
–
FRSR2
EYELMD
FM
SYELMD
B8ZS
B7
LPBK
SYMBOL
POSITION
NAME AND DESCRIPTION
–
CCR.7
Reserved, must be 0 for proper operation.
FRSR2
CCR.6
Function of REC Status Register 2.
0 = Detected B8ZS code words reported at RSR.2.
1 = COFA (Change-of-Frame Alignment) reported at RSR.2 when last re-
sync resulted in change of frame or multiframe alignment.
EYELMD
CCR.5
193E Yellow Mode Select.
0 = Yellow alarm is a repeating pattern set of 00 hex and FF hex.
1 = Yellow alarm is a 0 in the bit 2 position of all channels.
FM
CCR.4
Frame Mode Select.
0 = D4 (193S, 12 frames/superframe).
1 = Extended (193E, 24 frames/superframe).
SYELMD
CCR.3
193S Yellow Mode Select. Determines yellow alarm type to be transmitted
and detected while in 193S framing. If set, yellow alarms are a 1 in the S-bit
position of frame 12; if cleared, yellow alarm is a 0 in bit 2 of all channels.
Does not affect 193E yellow alarm operation.
B8ZS
CCR.2
Bipolar eight zero substitution.
0 = No B8ZS.
1 = B8ZS enabled.
(Note: This bit must be set to 0 when CCR.1=1)
B7
CCR.1
Bit seven zero suppression. If CCR.1=1, channels with an all zero con-
tent will be transmitted with bit 7 forced to 1. If CCR.1=0, no bit 7 stuffing
occurs.
(Note: This bit must be set to 0 when CCR.2=1)
LPBK
CCR.0
Loopback. When set, the device internally loops output transmit data into
the incoming receive data buffers and TCLK is internally substituted for
RCLK.
LOOPBACK (Refer to Figure 4)
Enabling loopback will typically induce an out-of-frame
(OOF) condition. If appropriate bits are set in the receive
control register, the receiver will resync to the looped
transmit frame alignment. During the looped condition,
the transmit outputs (TPOS, TNEG) will transmit un-
framed all 1’s. All operating modes (B8ZS, alarm,
signaling, etc.) except for blue alarm transmission are
available in loopback.
BIT SEVEN STUFFING
Existing systems meet 1’s density requirements by forc-
ing bit 7 of all zero channels to 1. Bit 7 stuffing is globally
enabled by asserting bit CCR.1 and may be disabled on
an individual channel basis by setting appropriate bits in
TTR1–TTR3. Bit 7 stuffing and B8ZS modes should not
be enabled simultaneously. Enabling both results in
LOS.