Motorola MPC823e - Page 892

Communication Processor Module
16-438 MPC823e REFERENCE MANUAL MOTOROLA
SPI
COMMUNICATION
16
PROCESSOR MODULE
16.12.3.2 SPI PARAMETER RAM MEMORY MAP. The SPI parameter RAM area begins
at the SPI base address and is used for the general SPI parameters. Notice that it is similar
to the SCCx general-purpose parameter RAM. You must initialize certain parameter RAM
values before the serial peripheral interface is enabled. The communication processor
module initilizes the other values. Once initialized, the parameter RAM values do not usually
need to be accessed by your software. They only need to be modified when there is no serial
peripheral interface activity in progress.
• RBASE and TBASE—The dual-port RAM starts receiving and transmitting data for the
RX and TX buffer descriptors in the RBASE and TBASE entries. They provide a great
deal of flexibility for partitioning buffer descriptors for a serial peripheral interface. You
must initialize these entries before enabling the corresponding channel. You must not
configure the SPI buffer descriptor tables to overlap with the tables of the USB, SMCx,
and SCCx or erratic operation will occur. RBASE and TBASE must contain a value that
is divisible by eight.
Table 16-39. SPI Parameter RAM Memory Map
ADDRESS NAME WIDTH DESCRIPTION
SPI Base + 00 RBASE Half-word RX Buffer Descriptor Base Address
SPI Base+ 02 TBASE Half-word TX Buffer Descriptor Base Address
SPI Base+ 04 RFCR Byte RX Function Code
SPI Base+ 05 TFCR Byte TX Function Code
SPI Base+ 06 MRBLR Half-word Maximum Receive Buffer Length
SPI Base+ 08 RSTATE Word RX Internal State
SPI Base+ 0C RPTR Word RX Internal Data Pointer
SPI Base + 10 RBPTR Half-word RX Buffer Descriptor Pointer
SPI Base + 12 RCNT Half-word RX Internal Byte Count
SPI Base + 14 RTMP Word RX Temp
SPI Base + 18 TSTATE Word TX Internal State
SPI Base + 1C TPTR Word TX Internal Data Pointer
SPI Base + 20 TBPTR Half-word TX Buffer Descriptor Pointer
SPI Base + 22 TCNT Half-word TX Internal Byte Count
SPI Base + 24 TTMP Word TX Temp
NOTE: You are only responsible for initializing the items in bold.
SPI Base = (IMMR & 0xFFFF0000) + 0x3D80.
SCCx Ethernet parameter RAM space overlaps the SPI parameter RAM space. The address range
for SCCx space is 0x1000 through 0x1CA3. You need a microcode patch to run SPI and Ethernet
concurrently.