DS26514 4-Port T1/E1/J1 Transceiver
19-5856; Rev 4; 5/11
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9.9.5.3 Legacy T1 Transmit FDL
It is recommended that the DS26514’s built-in BOC or HDLC controllers be used for most applications requiring
access to the FDL.
Table 9-21 shows the registers related to control of the transmit FDL.
Table 9-21. Registers Related to T1 Transmit FDL
REGISTER
FRAMER 1
ADDRESSES
FUNCTION
162h
FDL code used to insert transmit FDL.
182h
Defines the source of the FDL.
Transmit Latched Status Register 2
(TLS2)191h
Transmit FDL empty bit.
Transmit Interrupt Mask Register 2
(TIM2)1A1h
Mask bit for TFDL empty.
Note: The addresses shown above are for Framer 1. Addresses for Framers 2 to 4 can be calculated using the following: Framer n = (Framer 1
address + (n - 1) x 200hex), where n = 2 to 4 for Framers 2 to 4.
When enabled with
T1.TCR2.7, the transmit section will shift out into the T1 data stream, either the FDL (in the
ESF framing mode) or the Fs bits (in the D4 framing mode) contained in the Transmit FDL Register
(T1TFDL).
When a new value is written to the
T1TFDL, it will be multiplexed serially (LSB first) into the proper position in the
outgoing T1 data stream. After the full eight bits has been shifted out, the framer will signal the host controller that
the buffer is empty and that more data is needed by setting the
TLS2.4 bit to a one.
INTB will also toggle low if
enabled via
TIM2.4. The user has 2ms to update the
T1TFDL with a new value. If the
T1TFDL is not updated, the
old value in the
T1TFDL register will be transmitted once again. Note that in this mode, no zero stuffing will be
applied to the FDL data. It is strongly suggested that the HDLC controller be used for FDL messaging applications.
In the D4 framing mode, the framer uses the
T1TFDL register to insert the Fs framing pattern. To accomplish this
the
T1TFDL register must be programmed to 1Ch and
T1.TCR2.7 should be set to 0 (source Fs data from the
The
T1TFDL register contains the Facility Data Link (FDL) information that is to be inserted on a byte basis into the
outgoing T1 data stream. The LSB is transmitted first. In D4 mode, only the lower six bits are used.
9.9.5.4 Legacy T1 Receive FDL
It is recommended that the DS26514’s built-in BOC or HDLC controllers be used for most applications requiring
access to the FDL.
Table 9-22 shows the registers related to the receive FDL.
Table 9-22. Registers Related to T1 Receive FDL
REGISTER
FRAMER 1
ADDRESSES
FUNCTION
062h
FDL code used to receive FDL.
Receive Latched Status Register
7(RLS7)096h
Receive FDL full bit is in this register.
Receive Interrupt Mask Register
7(RIM7)0A6h
Mask bit for RFDL full.
Note: The addresses shown above are for Framer 1. Addresses for Framers 2 to 4 can be calculated using the following: Framer n = (Framer 1
address + (n - 1) x 200hex), where n = 2 to 4 for Framers 2 to 4.
In the receive section, the recovered FDL bits or Fs bits are shifted bit-by-bit into the Receive FDL Register
(T1RFDL). Since the
T1RFDL is 8 bits in length, it will fill up every 2ms (8 times 250
s). The framer will signal an
external controller that the buffer has filled via the
RLS7.2 bit. If enabled via
RIM7.2, the
INTB pin will toggle low
indicating that the buffer has filled and needs to be read. The user has 2ms to read this data before it is lost. Note
that no zero destuffing is applied to the for the data provided through the
T1RFDL register. The
T1RFDL register
reports the incoming Facility Data Link (FDL) or the incoming Fs bits. The LSB is received first. In D4 framing
mode,
T1RFDL updates on multiframe boundaries and reports only the Fs bits.