2.0 Circuit Description
2.4 Transmitter
CX28394/28395/28398
Quad/x16/Octal—T1/E1/J1 Framers
2.4.2.7 PRM Generator
In T1 applications, Performance Report Messages (PRMs) are HDLC messages
containing path identification and performance monitoring information. If
automatic performance report insertion is selected [AUTO_PRM; addr 0AA], a
performance report is generated each second and begins transmitting coincident
with the one-second timer interrupt [ONESEC; addr 005]. The PRM is sent
immediately if the processor sets SEND_PRM bit in the Performance Report
Message register [PRM; addr 0AA]. All performance monitoring fields of the
message are automatically filled in when a PRM is generated. The remaining
PRM bit fields are application-specific and can be configured using the
Performance Report Message register.
For limited systems, the automatic PRM generation off-loads a significant
portion of CPU bandwidth.
The Transmit Bit-Oriented Protocol (TBOP) transceiver sends BOP messages in
T1 applications, including ESF Yellow Alarm. These messages consist of
repeated 16-bit patterns with an embedded 6-bit codeword, as shown in this
example:
0xxxxxx0 11111111 (transmitted right to left)
[543210] TBOP = 6-bit codeword
2.4.2.8 TBOP
Transceiver
The TBOP is configured to operate over the same channel selected by Data
Link #1 [DL1_TS; addr 0A4]. The TBOP channel must be configured to operate
over the FDL channel in order for TBOP to convey Priority, Command, and
Response codeword messages according to ANSI T1.403, Section 9.4.1. The
precedence of transmitted BOP messages with respect to current DL1 transmit
activity is configurable using the Transmit BOP mode bits [TBOP_MODE[1,0];
addr 0A0]. BOP messages can also be transmitted during E1 mode, although the
16-bit codeword pattern has not currently been adopted as an E1 standard. The
length of the BOP message [TBOP_LEN[1,0]; addr 0A0] can be set to a single
pattern, 10 patterns, 25 patterns, or continuous.
BOP codewords are transmitted by writing to the Transmit BOP Codeword
[TBOP; addr 0A1]. The real-time status of the codeword transmission can be
monitored using TBOP_ACTIVE in the BOP Status register [BOP_STAT;
addr 0A3]. A TBOP Transmit interrupt is available in the Data Link 1 Interrupt
Status register [ISR2; addr 009] to indicate that a codeword has begun
transmission and the next codeword may be written to TBOP.
2.4.3 Sa-Byte Overwrite Buffer
There are five transmit Sa-Byte buffers [TSA4 to TSA8; addr 07B to 07F]. The
Sa-Byte buffers insert Sa-bits into the odd frames of TS0. The entire group of 40
bits is sampled every 16 frames coincident with the Transmit Multiframe bit
interrupt boundary [TMF; addr 008]. Bit 0 from each TSA register is then
inserted during frame 1, bit 1 is inserted during frame 3, bit 2 during frame 5, and
so on, which gives the processor up to 2 ms after TMF interrupt to write new
Sa-Byte buffer values. Transmit Sa-bits maintain a fixed relationship to the
transmit CRC multiframe. Each of the 5 Sa-Byte transmit buffers can be
individually enabled using the Manual Sa-Byte Transmit Enable in Transmit
Manual Sa-Byte/FEBE Configuration register [TMAN; addr 074].
2-46
Conexant
100054E
CONEXANT [ CONEXANT SYSTEMS, INC ]
