MC68LC302 Datasheet, PDF (79/169 Pages) Motorola, Inc – Low Power Integrated Multiprotocol Processor Reference Manual

Communications Processor (CP)
Table 4-3. Autobaud Specific Parameter
Address
SCC Base + 9C *
SCC Base + 9E
SCC Base + A0
SCC Base + A2 *
SCC Base + A4 *
SCC Base + A6 *
SCC Base + A8 *
SCC Base + AA *
SCC Base + AC *
SCC Base + AE
SCC Base + B0 *
SCC Base + B2 *
SCC Base + B4 *
SCC Base + B6 *
SCC Base + B8 *
SCC Base + BA *
SCC Base + BC *
SCC Base + BE *
Name
MAX_IDL
MAX_BIT
NOM_START
PAREC
FRMEC
NOSEC
BRKEC
ABCHR1
ABCHR2
RCCR
CHARACTER1
CHARACTER2
CHARACTER3
CHARACTER4
CHARACTER5
CHR6/RxPTR
CHR7RxPTR
CHR8/TxBD
Width
Description
Word Maximum IDLE Characters
Word Current Maximum START Bit Length
Word Current Nom. START Bit (used to determine baud rate)
Word Receive Parity Error Counter
Word Receive Framing Error Counter
Word Receive Noise Counter
Word Receive Break Error Counter
Word User Defined Character1
Word User Defined Character2
Word Receive Control Character Register
Word CONTROL Character1
Word CONTROL Character2
Word CONTROL Character3
Word CONTROL Character4
Word CONTROL Character5
Word CONTRChar6/MSW of pointer to external Rx Buffer
Word CONTRChar7/LSW of pointer to external Rx Buffer
Word CONTROL Character8/Transmit BD
* These values should be initialized by the user (M68000 core).
Note the new parameters that have been added to the table. They are MAX_BIT,
NOM_START, ABCHR1, ABCHR2, RxPTR (2 words), and TxBD. These parameters are
of special importance to the autobaud controller. They must be written prior to issuing the
Enter_Baud_Hunt command.
When the channel is operating in the autobaud hunt mode, the MAX_BIT parameter is used
to hold the current maximum START bit length. The NOM_START location contains the cur-
rent nominal start from the lookup table. After the autobaud is successful and the first char-
acter is matched, the user should use the NOM_START value from the autobaud specific
parameter RAM to determine which baud rate from the lookup table was detected. Also the
Tx internal data pointer (at offset SCC Base + 94) will point to the last character received
into external data buffer.
NOTE
When the channel is operating in the UART mode, the
NOM_START_/BRKCR is used as the break count register and
must be initialized before a STOP_TRANSMIT command is is-
sued.
The characters ABCHR1 and ABCHR2 are the autobaud characters that should be
searched for by the autobaud controller. Typically these are ‘a’ and ‘A’ (i.e. $0061 and
$0041) if using the Hayes command set. These characters must be odd in order for the auto-
baud controller to correctly determine the length of the START bit. Characters are transmit-
ted and received least significant bit first, so the autobaud controller detects the end of the
START bit by the least significant bit of the character being a ‘1’.
4-12
MC68LC302 REFERENCE MANUAL
MOTOROLA