____________________________________________________ DS34T101, DS34T102, DS34T104, DS34T108
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specify the 8-bit idle code for each channel and the
TCICE registers enable idle code insertion on a per-channel
basis.
10.11.13 Digital Milliwatt Code Generation
The Rx digital milliwatt registers
(RDMWE) specify which of the Rx E1/T1 channels should be overwritten with a
digital milliwatt code. The digital milliwatt code is an 8-byte repeating pattern that represents a 1kHz sine wave
(1E/0B/0B/1E/9E/8B/8B/9E). Each bit in the
RDMWE registers represents one channel. If a bit is set to a one, then
the Rx data in that channel is replaced with the digital milliwatt code. The
TDMWE registers perform the same
function in the transmit formatter.
10.11.14 In-Band Loop Code Generation and Detection (T1 Only)
10.11.14.1 Loop Code Generation
The transmit formatter can generate a repeating bit pattern from one to eight bits or 16 bits in length. This function
is available only in T1 mode.
To transmit a pattern, load the pattern to be sent into the transmit code definition registers
(TCD1 and
TCD2) and
specify the length of the pattern in
TCR4.TC. When generating a 1-, 2-, 4-, 8-, or 16-bit pattern, both transmit code
definition registers must be filled with the proper code. Generation of a 3-, 5-, 6-, or 7-bit pattern only requires
TCD1 to be filled. After these register fields are loaded, the pattern is transmitted as long as
TCR3.TLOOP=1.
Normally (unless the formatter is programmed to not insert the F-bit position) the formatter overwrites the repeating
pattern once every 193 bits to insert the F-bit.
As an example, to transmit the standard “l(fā)oop up” code for channel service units (CSUs), which is a repeating
pattern of ...10000100001..., set
TCD1 = 0x80,
TCR4.TC=00, and
TCR3.TLOOP=1.
Table 10-56. Registers Related to T1 In-Band Loop Code Generator
Register Field
Description
Functions
Page
Transmit Code Definition Register 1
pattern to be sent
Transmit Code Definition Register 2
pattern to be sent
Transmit Control Register 3
enable loop code transmission
Transmit Control Register 4
code length
10.11.14.2 Loop Code Detection
The Rx framer can detect a repeating bit pattern from one to eight bits or 16 bits in length. This function is available
only in T1 mode.
The framer has three programmable pattern detectors. Typically, two of the detectors are used for “l(fā)oop up” and
“l(fā)oop down” code detection. The CPU writes the codes to be detected into the Rx up code definition registers
each pattern into the
RIBCC register. The third detector is considered “spare” (i.e. extra). and is configured and
controlled by the
RSCD1/RSCD2 and
RSCC registers. When detecting a 16-bit pattern, both Rx code definition
registers are used together to form a 16-bit word. For 8-bit patterns both Rx code definition registers are loaded
with the same value. Detection of a 1-, 2-, 3-, 4-, 5-, 6-, and 7-bit pattern only requires the first Rx code definition
register to be filled. The framer detects repeating pattern codes in both framed and unframed data streams with bit
error rates as high as 10E–2. The detectors are capable of handling both F-bit inserted and F-bit overwrite
patterns. Writing the least significant byte of a Rx code definition register pair resets the integration period for that
detector. The code detector has a nominal integration period of 48ms. This means that after about 48ms of
receiving a valid code, the associated status bit (LUP, LDN, and LSP) is set to a one. Note that both real-time
status bits and latched status bit are available for LUP, LDN and LSP (
RRTS3-T1 and
RLS3-T1). Normally codes
are sent for a period of 5 seconds. It is recommend that the CPU poll the framer every 50ms to 100ms until 5
seconds has elapsed to ensure that the code is continuously present.