
DS26518 8-Port T1/E1/J1 Transceiver 
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9.9.4.2.6 Receive-Signaling Freeze 
The signaling data in the four multiframe signaling buffers will be frozen in a known good state upon either a loss of 
synchronization (OOF event), carrier loss, or change of frame alignment. In T1 mode, this action meets the 
requirements of BellCore TR-TSY-000170 for signaling freezing. To allow this freeze action to occur, the RSFE 
control bit (
RSIGC
.1) should be set high. The user can force a freeze by setting the RSFF control bit (
RSIGC
.2) 
high. The RSIGF output pin provides a hardware indication that a freeze is in effect. The four multiframe buffer 
provides a three multiframe delay in the signaling bits provided at the RSIGn pin (and at the RSERn pin if receive-
signaling reinsertion is enabled). When freezing is enabled (RSFE = 1), the signaling data will be held in the last 
known good state until the corrupting error condition subsides. When the error condition subsides, the signaling 
data will be held in the old state for at least an additional 9ms (4.5ms in D4 framing mode, 6ms for E1 mode) before 
being allowed to be updated with new signaling data. 
The receive-signaling registers are frozen and not updated during a loss of sync condition. They will contain the 
most recent signaling information before the LOF occurred. 
9.9.4.3 Transmit SLC-96 Operation (T1 Mode Only) 
In an SLC-96-based transmission scheme, the standard Fs-bit pattern is robbed to make room for a set of 
message fields. The SLC-96 multiframe is made up of six D4 superframes, hence it is 72 frames long. In the 72-
frame SLC-96 multiframe, 36 of the framing bits are the normal Ft pattern and the other 36 bits are divided into 
alarm, maintenance, spoiler, and concentrator bits as well as 12-bits of the normal Fs pattern. Additional SLC-96 
information can be found in BellCore document TR-TSY-000008. Registers related to the transmit FDL are shown 
in 
Table 9-18
. 
Table 9-18. Registers Related to SLC-96 
FRAMER 1 
ADDRESSES 
REGISTER 
FUNCTION 
Transmit FDL Register (
T1TFDL
) 
162h 
For sending messages in transmit SLC-96 Ft/Fs 
bits. 
Registers that control the SLC-96 overhead 
values. 
Transmit control for data selection source for the 
Ft/Fs bits. 
Status bit for indicating transmission of data link 
buffer. 
Transmit SLC-96 Data Link Registers 1 
to 3 (
T1TSLC1
:
T1TSLC3
) 
164h, 165h, 166h 
Transmit Control Register 2 
T1.TCR2
) 
182h 
Transmit Latched Status Register 1 
(
TLS1
) 
190h 
Receive SLC-96 Data Link Registers 1 
to 3 (
T1RSLC1
:
T1RSLC3
) 
064h, 065h, 066h 
— 
Receive Latched Status Register 7 
(
RLS7
) 
Note: 
The addresses shown above are for Framer
1. Addresses for Framers 2 to 8 can be calculated using the following: Framer
n = (Framer
1 
address + (n - 1) x 200hex), where n = 2 to 8 for Framers 2 to 8. 
096h 
Receive SLC-96 alignment event. 
The 
T1TFDL
 register is used to insert the SLC-96 message fields. To insert the SLC-96 message using the 
T1TFDL
 register, the user should configure the DS26518 as shown below: 
 
T1.TCR2
.6 (TSLC96) = 1 
Enable Transmit SLC-96. 
 
T1.TCR2
.7 (TFDLS) = 0 
Source FS bits via TFDL or SLC-96 formatter. 
 
TCR3
.2 (TFM) = 1  
D4 framing mode. 
 
TCR1
.6 (TFPT) = 0  
Do not “pass through” TSERn F-bits. 
The DS26518 will automatically insert the 12-bit alignment pattern in the Fs bits for the SLC-96 data link frame. 
Data from the 
T1TSLC1
–3 will be inserted into the remaining Fs-bit locations of the SLC-96 multiframe. The status 
bit TSLC96 located at 
TLS1
.4 will set to indicate that the SLC-96 data link buffer has been transmitted and that the 
user should write new message data into 
T1TSLC1
–3. The host will have 9ms after the assertion of 
TLS1
.4 to write 
the registers 
T1TSLC1
–3. If no new data is provided in these registers, the previous values will be retransmitted.