
3.0 Registers
CN8223
3.3 Configuration Control Registers
ATM Transmitter/Receiver with UTOPIA Interface
3-4
Conexant
100046D
one-second interval, the second read gives the current state of the status word and 
clears it. 
3.3  Configuration Control Registers
0x00—CONFIG_1 (Configuration Control Register 1) 
The CONFIG_1 register is located at address 0x00. This register sets chip parameters for both transmit and 
receive operations. The line interface type is set for both transmit and receive by bits 7
–
0. Valid combinations of 
bits 7
–
0 for the line interface type in this register are given in 
Table 3-3
.
Bit
Field 
Size
Name
Description
15
1
STS-1 Stuffing 
Option
Enables an alternate ATM mapping for STS-1 mode. If this bit is set, then 84 
columns of the SPE are available for ATM cell octets. If this bit is not set, then all 86 
columns of the SPE are available for ATM cell octets.
14
1
Source Loopback
Causes the receiver input to be taken from the transmitter output in all modes; the 
transmitter output is unaffected. This function allows the generation of 
self-diagnostic routines at system startup to ensure the health of the line/physical 
framing process. If an external framer mode is selected, the external framer needs to 
continue providing an input to TXSYI when source loopback is enabled. Source 
loopback does not work in TAXI mode.
13
1
Enable One-Second 
Latching of Line 
Counters
Causes status indications in the line/PHY counters (other than LCV) to be latched at 
one-second intervals. This interval is determined by successive rising clock edges to 
ONESECI. If an alarm condition is present during a one-second interval, it is 
available to be read on the successive interval. Otherwise, the status is latched and 
held until it is read. If this bit is set and the status word is read twice within a 
12
1
Enable One-Second 
Latching of Line 
Status
Causes status indications in the LINE_STATUS register to be latched at one-second 
intervals. The one-second interval is determined by successive rising clock edges to 
ONESECI. If an alarm condition is present during a one-second interval, it is 
available to be read on the successive interval. Otherwise, the status is latched and 
held until it is read. If this bit is set and the status word is read twice within a 
one-second interval, the second read gives the current state of the status word and 
clears it. 
11
1
External 8 kHz 
Timing
Forces the transmit PLCP to be synchronized to an external 8 kHz timing reference 
rather than to the received PLCP reference. This control bit is meaningful only in 
57-octet DS3 and E3 formats.
10
1
Receiver Hold 
Enable
Allows the RCV_HLD input to disable cell processing. Internal cell receiver functions 
will operate, but no segments will be accepted by the cell validation state machine or 
output on the FIFO ports.
9
1
Enable Cell 
Scrambler
Enables the x
43 
+ 1 scrambler (required for 53-octet direct mapping) for cell 
payload. 
8
1
Disable LOCD
Allows cell validation and error counting to continue when cell delineation is lost (via 
either PLCP or HEC).