Motorola MPC823e - Page 637

Communication Processor Module
MOTOROLA MPC823e REFERENCE MANUAL 16-183
SCCs
COMMUNICATION
16
PROCESSOR MODULE
• RBASE and TBASE—The dual-port RAM starts receiving and transmitting data for the
SCCx buffer descriptors in the RBASE and TBASE entries. They allow more flexibility
in partitioning the SCCx buffer descriptors. By selecting RBASE and TBASE entries for
a serial communication controller and by setting the W bit in the last buffer descriptor in
each buffer descriptor list, you can select how many buffer descriptors to allocate for
the transmit and receive side of a serial communication controller. However, you must
initialize these entries before enabling the corresponding channel.
Table 16-24. SCCx Parameter RAM Memory Map For All Protocols
ADDRESS NAME WIDTH DESCRIPTION
SCCx Base + 00 RBASE Half-word RX Buffer Descriptor Base Address
SCCx Base + 02 TBASE Half-word TX Buffer Descriptor Base Address
SCCx Base + 04 RFCR Byte RX Function Code
SCCx Base + 05 TFCR Byte TX Function Code
SCCx Base + 06 MRBLR Half-word Maximum Receive Buffer Length
SCCx Base + 08 RSTATE Word RX Internal State
SCCx Base + 0C RPTR Word RX Internal Data Pointer
SCCx Base + 10 RBPTR Half-word RX Buffer Descriptor Pointer
SCCx Base + 12 RCNT Half-word RX Internal Byte Count
SCCx Base + 14 RTMP Word RX Temp
SCCx Base + 18 TSTATE Word TX Internal State
SCCx Base + 1C TPTR Word TX Internal Data Pointer
SCCx Base + 20 TBPTR Half-word TX Buffer Descriptor Pointer
SCCx Base + 22 TCNT Half-word TX Internal Byte Count
SCCx Base + 24 TTMP Word TX Temp
SCCx Base + 28 RCRC Word Temp Receive CRC
SCCx Base + 2C TCRC Word Temp Transmit CRC
SCCx Base + 30 First Word of Protocol-Specific Area
SCCx Base + xx Last Word of Protocol-Specific Area
NOTE: You are only responsible for initializing the items in bold.
SCCx Base = (IMMR & 0xFFFF0000) + 0x3D00 (SCC2) and 0x3E00 (SCC3).
Note: RBASE and TBASE must contain a value that is divisible by eight.