MPC8280 datasheet(1292/1386 Pages) FREESCALE

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Serial Peripheral Interface (SPI)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

39-8

Freescale Semiconductor

Figure 39-6. SPI Transfer Format with SPMODE[CP] = 1

39.4.1.1

SPI Examples with Different SPMODE[LEN] Values

The examples below show how SPMODE[LEN] is used to determine character length. To help map the

process, the conventions shown in Table 39-2 are used in the examples.

Once the data string image is determined, it is always transmitted byte by byte with the lsb of the

most-significant byte sent first. For all examples below, assume the memory contains the following binary

image:

msb

ghij_klmn__opqr_stuv

lsb

Example 1

with LEN=4 (data size=5), the following data is selected:

msb

xxxj_klmn__xxxr_stuv

lsb

with REV=0, the data string image is:

msb

j_klmn__r_stuv

lsb

the order of the string appearing on the line, a byte at a time is:

first

nmlk_j__vuts_r

last

with REV=1,the string has each byte reversed, and the data string image is:

msb

nmlk_j__vuts_r

lsb

the order of the string appearing on the line, one byte at a time is:

first

j_klmn__r_stuv

last

Table 39-2. Example Conventions

Convention

Description

g–v

Binary symbols

Deleted bit

__ 1

1 Both __ and _ are used to aid readability.

Original byte boundary

_ 1

Original 4-bit boundary.

SPICLK

SPIMOSI

SPISEL

(From Master)

SPIMISO

(From Slave)

(CI = 0)

(CI = 1)

NOTE: Q = Undefined Signal.

msb

lsb

Qmsb

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