MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 238

• Manufacturer Part Number: MC68000
• Manufacturer: MOTOROLA [Motorola, Inc]

Communications Processor (CP)
The V.110 controller operates on the ISDN physical interface using either IDL or GCI (IOM-
2) over one of the B channels. NMSI and PCM physical interfaces are also possible. The
data synchronization register (DSR) should be programmed to 'xxxxxxx1 00000000'b to
achieve the proper frame synchronization (see 4.5.4 SCC Data Synchronization Register
(DSR)).
4.5.15.5 V.110 Programming Model
The M68000 core configures each SCC to operate in one of the protocols by the MODE1–
MODE0 bits in the SCC mode register. If MODE1–MODE0 = 10, the synchronous link DDC-
MP protocol is selected. The V.110 bit should also be set in the DDCMP mode register. The
V.110 controller uses the same basic data structure as the DDCMP controller, the same
command set, and the same event and mask registers for interrupt generation.
4.5.15.6 Error-Handling Procedure
The V.110 controller reports frame reception and transmission error conditions using the
channel buffer descriptors (BDs) and the V.110 event register.
Transmission Errors:
Reception Errors:
4.5.15.7 V.110 Receive Buffer Descriptor (Rx BD)
The CP reports information about the received data for each buffer using the BDs. The Rx
BD is shown in Figure 4-40. The CP closes the current buffer, generates a maskable inter-
rupt, and starts to receive data in the next buffer after any of the following events:
4-118
1. Transmitter Underrun. When this error occurs, the channel terminates buffer transmis-
1. Overrun Error. The V.110 controller maintains an internal three-byte length FIFO for
2. Synchronization Error. A synchronization error is detected by the V.110 controller
• Receiving of 10 bytes (80-bit frame)
• Detecting of an error
• Issuing the ENTER HUNT MODE command
sion, closes the buffer, sets the underrun (UN) bit in the BD, and generates the trans-
mit error (TXE) interrupt (if enabled). The channel will resume transmission after the
reception of the RESTART TRANSMIT command. The FIFO size is three bytes.
receiving data. When the receive FIFO overrun error occurs, the channel writes the
received data byte to the internal FIFO on top of the previously received byte (the pre-
vious data byte is lost). Then the channel closes the buffer, sets the overflow (OV) bit
in the BD, and generates the receive frame (RXF) interrupt (if enabled). The channel
will automatically enter hunt mode.
when the MSB of every byte is not one. When this error occurs, the channel writes the
received byte to the buffer and continues to receive the V.110 frame. When the frame
ends, the channel closes the buffer, sets the synchronization error (SE) bit in the BD,
and generates the RXF interrupt (if enabled). The channel will automatically enter the
hunt mode.
MC68302 USER’S MANUAL
MOTOROLA