MPC823 datasheet(57/74 Pages) MOTOROLA

57 / 74 page

Communication Processor Module

MOTOROLA

MPC823 REFERENCE MANUAL

16-435

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.

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