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CS62180B-IL

T1 Framer

Cirrus Logic 

CS62180A

CS62180B

7 (MSB)

FM1

See Fig. 4b

6

FRSR2

0 B8ZS

1 COFA

5

4

EYELMD FM

0 FDL

1 Bit 2

See Fig. 4b

3

YELS

0 Bit 2

1 S-bit

2

B8ZS

0 Disable

1 Enable

1

0 (LSB)

B7 LPBK

0 Transparent 0 Normal

1 B7 Stuffing 1 Loopback

Figure 4a. Common Control Register (CCR)

Common Control Register

The Common Control Register (CCR) deter-

mines global operating characteristics common

to both the transmitter and receiver. It currently

provides for selection of the framing mode

(193S, 193E, SLC-96® or T1DM), the format of

yellow alarms, the zero suppression format (B7

or B8ZS), loopback operation, and control of

output to RSR.2. In the CS62180A, CCR.7 is re-

served for future use, and should always be set 0

for proper operation. See Figure 4a for an over-

view of the CCR.

Loopback

CCR.0: LPBK

Setting LPBK (CCR.0) to "1" puts the

CS62180A and CS62180B into loopback mode.

While in loopback, the TPOS/TNEG and TCLK

outputs are internally rerouted directly to the

RPOS/RNEG and RCLK inputs, while an un-

framed, all "1’s" stream is output on the

TPOS/TNEG pins. All operating modes, except

blue alarm transmission, remain functional dur-

ing loopback. Note that enabling loopback will

usually invoke an out-of-frame (OOF) error un-

til the receiver can resync to the new framing

alignment. See the section on the Receive Con-

trol Register (RCR) for a description of the

resync options available.

with all zeros to be transmitted with bit 7 (2nd

LSB) forced to a "1". B7 mode only affects the

transmitter, the receiver does not decode B7.

Note that bit 7 stuffing can be disabled on an

individual channel basis for clear channel trans-

mission via the Transmit Transparent Registers

TTR1 - TTR3 (see description of transmitter

which follows).

B8ZS coding operates independent of channel

boundaries, and is transparent to all other func-

tions. When using B8ZS, the final transmission

stream is examined before transmission, and

any eight consecutive zeros will be replaced

with a B8ZS code word before transmission.

CS62180A Only: If B8ZS (CCR.2) is set to a

"1", B8ZS zero substitution will be enabled in

both the transmitter and receiver. Incoming

B8ZS codes will be intercepted by the receiver

and replaced with 8 zeros before being proc-

essed by the rest of the receive side.

CS62180B Only: If B8ZS (CCR.2) is set to a

"1", B8ZS zero substitution will be enabled in

the transmitter. Independent of the setting of

CCR.2, any incoming B8ZS codes will be inter-

cepted by the receiver and replaced with 8

zeros before being processed by the rest of the

receive side. The receiver is always capable of

receving either AMI or B8ZS encoded data.

Zero Suppression

CCR.1: B7

CCR.2: B8ZS

Note: For T1DM, CCR.1 and CCR.2 should be

set to a "0" since DDS® equipment assures a 1-

in-8 one’s density.

B7 and B8ZS select the zero suppression mode.

Setting B7 (CCR.1) to "1" will enable bit 7

zero substitution. This causes any channel word

10

DS225PP1

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