Chapter 4 Memory

START

 

 

 

 

 

 

 

 

 

 

 

 

 

PRDIV8 = 0 (reset)

 

 

 

 

 

 

yes

 

 

 

 

 

bus_clock

 

ALL PROGRAM AND ERASE

0.3MHz?

 

 

COMMANDS IMPOSSIBLE

no

bus_clock no

12.8MHz?

 

 

yes

 

 

 

 

 

 

 

set PRDIV8 = 1

 

PRDCLK = bus_clock

PRDCLK = bus_clock/8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PRDCLK[kHz]/200 no an integer?

yes

set FDIV[5:0] = INT(PRDCLK[kHz]/200)

 

 

 

set FDIV[5:0] = PRDCLK[kHz]/200-1

 

 

 

 

FCLK = (PRDCLK)/(1+FDIV[5:0])

 

 

 

 

Note:

 

 

 

 

END

FCLK is the clock of the flash timing control block

INT(x) is the integer part of x (e.g. INT(4.323) = 4)

 

 

Figure 4-9. Determination Procedure for PRDIV8 and FDIV Bits

4.5.1.2Command Write Sequence

The flash command controller supervises the command write sequence to execute program, erase, and erase verify algorithms.

Before starting a command write sequence, the FACCERR and FPVIOL flags in the FSTAT register must be clear and the FCBEF flag must be set (see Section 4.4.2.5).

A command write sequence consists of three steps that must be strictly adhered to with writes to the flash module not permitted between the steps. However, flash register and array reads are allowed during a command write sequence. The basic command write sequence is as follows:

1. Write to a valid address in the flash array memory.

MCF51QE128 MCU Series Reference Manual, Rev. 3

Freescale Semiconductor

79

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Freescale Semiconductor MCF51QE128RM manual Command Write Sequence, Start, ALL Program and Erase, Commands Impossible, End