ds21ft40 Maxim Integrated Products, Inc., ds21ft40 Datasheet - Page 58

• Manufacturer Part Number: ds21ft40
• Description: Ds21ft40 Four X Three 12 Channel E1 Framer
• Manufacturer: Maxim Integrated Products, Inc.

Transmit a HDLC Message
1. Make sure HDLC controller is done sending any previous messages and is current sending flags by
2. Enable either the THALF or TNF interrupt.
3. Read THIR to obtain TFULL status.
4. Repeat step 3.
5. Wait for interrupt, skip to step 3.
6. Disable THALF or TNF interrupt and enable TMEND interrupt.
7. Wait for an interrupt, then read TUDR status bit to make sure packet was transmitted correctly.
14.4 HDLC REGISTER DESCRIPTION
HCR: HDLC CONTROL REGISTER (Address=B0 Hex)
(MSB)
SYMBOLS
checking that the FIFO is empty by reading the TEMPTY status bit in the THIR register.
–
TCRCD
TEOM
TABT
TZSD
RHR
THR
TFS
A. If TFULL=0, then write a byte into the FIFO and skip to next step (special case occurs when
the last byte is to be written, in this case set TEOM=1 before writing the byte and then skip to
step 6)
B. If TFULL=1, then skip to step 5
–
RHR
POSITION
HCR.7
HCR.6
HCR.5
HCR.4
HCR.3
HCR.2
HCR.1
HCR.0
TFS
NAME AND DESCRIPTION
Not Assigned. Should be set to zero.
Receive HDLC Reset. A 0 to 1 transition will reset the receive
Transmit End of Message. Should be set to a one just before
HDLC controller. Must be cleared and set again for a
subsequent reset.
Transmit Flag/Idle Select.
0 = 7Eh.
1 = FFh.
Transmit HDLC Reset. A 0 to 1 transition will reset the
transmit HDLC controller. Must be cleared and set again for a
subsequent reset.
Transmit Abort. A 0 to 1 transition will cause the FIFO
contents to be dumped and one FEh abort to be sent followed
by 7Eh or FFh flags/idle until a new packet is initiated by
writing new data into the FIFO. Must be cleared and set again
for a subsequent abort to be sent.
the last data byte of a HDLC packet is written into the transmit
FIFO at THFR. The HDLC controller will clear this bit when
the last byte has been transmitted.
Transmit Zero Stuffer Defeat. Overrides internal enable.
0 = enable the zero stuffer (normal operation).
1 = disable the zero stuffer.
Transmit CRC Defeat.
0 = enable CRC generation (normal operation).
1 = disable CRC generation.
THR
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TABT
TEOM
TZSD
TCRCD
(LSB)
DS21FT40