Serial Communication Controllers (SCCs)
MOTOROLA
MC68360 USER’S MANUAL
7-141
including the parameter RAM. If the user desires to switch protocols or restore the
SCC receive parameters to their initial state, the INIT RX PARAMETERS command
may now be issued.
3. ENTER HUNT MODE command. This command is required if the INIT RX PARAME-
TERS command was not issued in step 2.
4. Set the ENR bit in the GSMR. Reception will now begin immediately using the Rx BD
pointed to by the RBPTR if the Rx BD E-bit is set.
7.10.14.4 SCC RECEIVER SHORTCUT SEQUENCE.
A shorter sequence is possible if
the user desires to reinitialize the receive parameters to the state they had after reset.
This sequence is as follows:
1. Clear the ENR bit in the GSMR.
2. INIT RX PARAMETERS command. Any additional modifications may now be made.
3. Set the ENR bit in the GSMR.
7.10.14.5 SWITCHING PROTOCOLS.
Sometimes the user desires to switch the protocol
that the SCC is executing (e.g., UART to HDLC) without resetting the board or affecting
any other SCC. This can be accomplished using only one command and a short num-
ber of steps:
1. Clear the ENT and ENR bits in the GSMR.
2. INIT TX AND RX PARAMETERS command. This one command initializes both trans-
mit and receive parameters. Any additional modifications may now be made in the
GSMR to change the protocol, etc.
3. Set the ENT and ENR bits in the GSMR. The SCC is enabled with the new protocol.
7.10.15 Saving Power
When the ENT and ENR bits of an SCC are cleared, that SCC consumes a minimal amount
of power.
7.10.16 UART Controller
Many applications need a simple method of communicating low-speed data between equip-
ment. The universal asynchronous receiver transmitter (UART) protocol is the de-facto stan-
dard for such communications. The term asynchronous is used because it is not necessary
to send clocking information with the data that is sent. UART links are typically 38400 baud
or less in speed and are character oriented (i.e., the smallest unit of data that can be cor-
rectly received or transmitted is a character). Typical applications of asynchronous links are
connections between terminals and computer equipment. Even in applications where syn-
chronous communications are required, the UART is often used for a local debugging port
to run board debugger software. The character format of the UART protocol is shown in Fig-
ure 7-46.