HFC-Smini Cologne Chip AG, HFC-Smini Datasheet - Page 13

• Manufacturer Part Number: HFC-Smini
• Manufacturer: Cologne Chip AG

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3.2
There is a transmit and a receive FIFO with HDLC-controller for each of the two B-channels, for the D-
channel and for the PCM interface in the HFC-S mini. Each FIFO has 128 bytes length in each direction.
Up to 7 frames can be stored in each FIFO.
The HDLC circuits are located on the S/T device side of the HFC-S mini. So always plain data is stored
in the FIFOs. Zero insertion and CRC checksum processing for receive and transmit data is done by the
HFC-S mini automatically.
A FIFO can be selected for access by writing its number in the FIFO select register (FIFO#).
The FIFOs are ring buffers. To control them there are some counters. Z1 is the FIFO input counter and
Z2 is the FIFO output counter.
Each counter points to a byte position in the SRAM. On a FIFO input operation Z1 is incremented. On an
output operation Z2 is incremented.
After every pulse on the F0IO signal two HDLC-bytes are written into the S/T interface (FIFOs with
even numbers) and two HDLC-bytes are read from the S/T interface (FIFOs with odd numbers).
D-channel data is handled in a similar way but only 2 bits are processed.
If Z1 = Z2 the FIFO is empty.
Additionally there are two counters F1 and F2 for every FIFO channel (3 bits for each channel). They
count the HDLC-frames in the FIFOs and form a ring buffer as Z1 and Z2 do, too.
F1 is incremented when a complete frame has been received and stored in the FIFO. F2 is incremented
when a complete frame has been read from the FIFO.
If F1 = F2 there is no complete frame in the FIFO.
When the RESET line is active or software reset is active Z1, Z2, F1 and F2 are all initialized to all 1s
(so Z-counters are initialized to 7Fh and F-counters are initialized to 07h).
The access to a FIFO is selected by writing the FIFO number into the FIFO select register (FIFO#).
*
Instead of the S/T interface also PCM bus is selectable for each B-channel (see CON_HDLC
register).
important!
FIFOs
Cologne
Chip