PEB20571 INFINEON [Infineon Technologies AG], PEB20571 Datasheet - Page 115

• Manufacturer Part Number: PEB20571
• Description: ICs for Communications
• Manufacturer: INFINEON [Infineon Technologies AG]

The Transmit Output Buffer is a 32 x 15 RAM because, in addition to each HDLC
channel, there is also a 7 bit status vector assigned to each channel stored in this buffer.
The DSP assigns each time slot used for transceiving an HDLC message to a different
address in the Receive/Transmit Input Buffers. The HDLCU decodes/encodes the time
slots into the corresponding addresses in the Receive/Transmit Output Buffers.
During every frame, two HDLCU activities are performed:
1. DSP access to the HDLCU
2. HDLCU encoding/decoding
At the beginning of a frame the DSP checks if the HDLCU is busy (HHOLD = ’0’). Note
that the DSP may only access the buffers and command RAM when DSPCTRL = ‘1’.
In the receive direction the DSP places HDLC message time slots to be processed from
the D-buffers into the Receive Input Buffer. Processed message time slot octets may be
read by the DSP from the Receive Output Buffer.
In the transmit direction the DSP places HDLC message time slots to be processed in
the Transmit Input Buffer. Processed time slots may be read from the Transmit Output
Buffer and placed into the D-Buffer of the IOMU, PCMU or TRANSIU from which they
will be transmitted during the next frame.
4.6.2
4.6.2.1
The first frame is used to reset the receive and transmit mechanisms of each channels.
1. The DSP asks for the HDLCU setup from the External Controller.
2. The DSP sets the bit DSPCTRL to ‘1’.
3. The DSP resets the receive mechanism and transmit mechanism of a channel by
4. The DSP sets DSPCTRL to ‘0’.
5. When the HDLCU finishes processing (HHOLD = ’1’), the HDLCU is initialized and is
4.6.2.2
In order to transmit a message the DSP must place a Start transmission command in the
appropriate address in the command RAM.
If CRC encoding is required, then the DSP must set bit 1 to ‘1’ in the command vector.
In the unshared flag mode, during the first frame a flag is transmitted over the channel.
After the flag has been transmitted, the HDLCU starts to transmit the message. In the
Preliminary Data Sheet
setting the RECRES flag of its command vector to ‘1’ and inserting an abort command.
The DSP also writes the setup of the HDLCU.
ready for use.
DSP Operation of the HDLCU
Initialization of the HDLCU
Transmitting a Message
4-31
Functional Description
PEB 20571
DELIC
2003-08