MAC7200 datasheet(656/976 Pages) FREESCALE

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DSPI Application Usage

MAC7200 Microcontroller Family Reference Manual, Rev. 2

578

Freescale Semiconductor

•

Fixed MUCts01650: Write on bus abort still writes register

•

DSPI runs directly from system (fast) clock (not programmable) instead of from peripheral (slow)

clock

•

Continuous chip select definition updated in the Block Guide (v0.26)

30.8

DSPI Application Usage

30.8.1

Enabling the DSPI

Before the DSPI can be used, it must be explicitly enabled by clearing the MDIS bit.

30.8.2

Baud Rate Calculation

Eqn. 30-1

Given the above Baud Rate equation, and the limitations of the fsys, PBR, DBR and BR settings, the

maximum baud rate is as follows:

NOTE

The above Baud Rate calculations apply to Master Mode only.

On the MAC71x1, fDSPI = fSYS/2. On the MAC72xx fDSPI = fSYS

Table 30-4. DSPI Maximum Baud Rate Parameters

Parameter

MAC71x1

MAC72xx

fsys

< 50MHz

< 70MHz

fdspi

< 25MHz

< 70MHz

PBR

2...7

DBR

DBR bit not available

0,1

2...32768

Maximum Baud Rate (DBR=0)

fdspi/4 = 6.25 Mb/s

fdspi/4 = 17.5 Mb/s

Maximum Baud Rate (DBR=1)

DBR bit not available

fdspi/2 = 35 Mb/s

Min. system clock frequency for 8 Mb/s

(DBR=0)

64 MHz

32 MHz

Min. system clock frequency for 8 Mb/s

(DBR=1)

DBR bit not available

16 MHz

Table 30-5. DSPI SCK Duty Cycle Calculation

DBR

CPHA

PBR

SCK Duty Cycle

any

50/50

BaudRate

fdspi

PBR

--------------

DBR

-----------------------

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