Datasheet

DS26518 8-Port T1/E1/J1 Transceiver
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Register Name:
TH256CR1
Register Description:
Transmit HDLC-256 Control Register 1
Register Address:
1500h + (20h x (n - 1)) : where n = 1 to 8
Bit # 7 6 5 4 3 2 1 0
Name — TPSD TFEI TIFV TBRE TDIE TFPD TFRST
Default 0 0 0 0 0 0 0 0
Bit 6: Transmit Packet Start Disable (TPSD). When 0, the transmit packet processor continues sending packets
after the current packet end. When 1, the transmit packet processor stops sending packets after the current packet
end.
Bit 5: Transmit FCS Error Insertion (TFEI). When 0, the calculated FCS (inverted CRC-16) is appended to the
packet. When 1, the inverse of the calculated FCS (noninverted CRC-16) is appended to the packet causing a FCS
error. This bit is ignored if transmit FCS processing is disabled (TFPD = 1).
Bit 4: Transmit Interframe Fill Value (TIFV). When 0, interframe fill is done with the flag sequence (7Eh). When 1,
interframe fill is done with all ones.
Bit 3: Transmit Bit Reordering Enable (TBRE). When 0, bit reordering is disabled. (The first bit transmitted is the
LSB of the transmit FIFO data byte TFD[0]). When 1, bit reordering is enabled. (The first bit transmitted is the MSB
of the transmit FIFO data byte TFD[7]).
Bit 2: Transmit Data Inversion Enable (TDIE). When 0, the outgoing data is directly output from packet
processing. When 1, the outgoing data is inverted before being output from packet processing.
Bit 1: Transmit FCS Processing Disable (TFPD). This bit controls whether a FCS is calculated and appended to
the end of each packet. When 0, the calculated FCS bytes are appended to the end of the packet. When 1, the
packet is transmitted without a FCS.
Bit 0: Transmit FIFO Reset (TFRST). When 0, the transmit FIFO resumes normal operations, however, data is
discarded until a start of packet is received after RAM power-up is completed. When 1, the transmit FIFO is
emptied, any transfer in progress is halted, the FIFO RAM is powered down, and all incoming data is discarded (all
TFDR register writes are ignored).
Register Name:
TH256CR2
Register Description:
Transmit HDLC-256 Control Register 2
Register Address:
1501h + (20h x (n - 1)) : where n = 1 to 8
Bit # 7 6 5 4 3 2 1 0
Name
— — —
TDAL4 TDAL3 TDAL2 TDAL1 TDAL0
Default 0 0 0 0 1 0 0 0
Bits 4 to 0: Transmit HDLC-256 Data Storage Available Level (TDAL[4:0]). These five bits indicate the
minimum number of bytes ([TDAL x 8] + 1) that must be available for storage (do not contain data) in the transmit
FIFO for HDLC-256 data storage to be available. For example, a value of 21 (15h) results in HDLC-256 data
storage being available (THDA = 1) when the transmit FIFO has 169 (A9h) bytes or more available for storage, and
HDLC-256 data storage not being available (THDA = 0) when the transmit FIFO has 168 (A8h) bytes or less
available for storage. Default value (after reset) is 128 bytes minimum available.