MPC8541ECPXALF datasheet(45/84 Pages) FREESCALE

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MPC8541E PowerQUICC™ III Integrated Communications Processor Hardware Specifications, Rev. 4

Freescale Semiconductor

CPM

10.3

CPM I2C AC Specification

Figure 29. CPM I2C Bus Timing Diagram

The following two tables are examples of I2C AC parameters at I2C clock value of 100k and 400k

respectively.

Table 35. I2C Timing

Characteristic

Expression

All Frequencies

Unit

Min

Max

SCL clock frequency (slave)

fSCL

0FMAX

(1)

Notes:

FMAX = BRGCLK/(min_divider*prescale. Where prescaler=25-I2MODE[PDIV]; and min_divider=12 if digital filter disabled

and 18 if enabled.

Example #1: if I2MODE[PDIV]=11 (prescaler=4) and I2MODE[FLT]=0 (digital filter disabled) then FMAX=BRGCLK/48

Example #2: if I2MODE[PDIV]=00 (prescaler=32) and I2MODE[FLT]=1 (digital filter enabled) then FMAX=BRGCLK/576

SCL clock frequency (master)

fSCL

BRGCLK/16512

BRGCLK/48

Bus free time between transmissions

tSDHDL

1/(2.2 * fSCL)-

Low period of SCL

tSCLCH

1/(2.2 * fSCL)-

High period of SCL

tSCHCL

1/(2.2 * fSCL)-

Start condition setup time2

tSCHDL

2/(divider * fSCL)

- (2)

2. divider = fSCL/prescaler.

In master mode: divider=BRGCLK/(fSCL*prescaler)=2*(I2BRG[DIV]+3)

In slave mode: divider=BRGCLK/(fSCL*prescaler)

Start condition hold time2

tSDLCL

3/(divider * fSCL)-

Data hold time 2

tSCLDX

2/(divider * fSCL)-

Data setup time2

tSDVCH

3/(divider * fSCL)-

SDA/SCL rise time

tSRISE

1/(10 * fSCL)s

SDA/SCL fall time

tSFALL

1/(33 * fSCL)s

Stop condition setup time

tSCHDH

2/(divider * fSCL)

Table 36. CPM I2C Timing (fSCL=100KHz)

Characteristic

Expression

Frequency = 100KHz

Unit

Min

Max

SCL clock frequency (slave)

fSCL

100

KHz

SCL clock frequency (master)

fSCL

100

KHz

Bus free time between transmissions

tSDHDL

4.7

μs

Low period of SCL

tSCLCH

4.7

μs

SCL

SDA

tSDHDL

tSCLCH

tSCHCL

tSCHDL

tSDLCL

tSCLDX

tSDVCH

tSRISE

tSFALL

tSCHDH

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