IMX53IEC datasheet(45/173 Pages) FREESCALE

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Electrical Characteristics

i.MX53 Applications Processors for Industrial Products, Rev. 6

Freescale Semiconductor

4.6.5

NAND Flash Controller (NFC) Parameters

This section provides the relative timing requirements among various signals of NFC at the module level,

in each operational mode.

Timing parameters in Figure 10, Figure 11, Figure 12, Figure 13, Figure 15, and Table 35 show the default

NFC mode (asymmetric mode) using two Flash clock cycles per one access of RE_B and WE_B.

Timing parameters in Figure 10, Figure 11, Figure 12, Figure 14, Figure 15, and Table 35 show symmetric

NFC mode using one Flash clock cycle per one access of RE_B and WE_B.

With reference to the timing diagrams, a high is defined as 80% of signal value and low is defined as 20%

of signal value. All parameters are given in nanoseconds. The BGA contact load used in calculations is

20 pF (except for NF16— 40 pF) and there is maximum drive strength on all contacts.

All timing parameters are a function of T, which is the period of the flash_clk clock (“enfc_clk” at system

level). This clock frequency can be controlled by the user, configuring CCM (SoC clock controller). The

clock is derived from emi_slow_clk after single divider.

Figure 34 demonstrates several examples of clock frequency settings.

NOTE

A potential limitation for minimum clock frequency may exist for some

devices. When the clock frequency is too low, the data bus capturing might

occur after the specified trhoh (RE_B high to output hold) period. Setting the

clock frequency above 25.6 MHz (that is, T = 39 ns) guaranties a proper

operation for devices having trhoh > 15 ns. It is also recommended that the

NFC_FREQ_SEL Fuse be set accordingly to initiate the boot with

33.33 MHz clock.

4 T

dpdref is the time period of the reference clock after predivider. According to the specification, the maximum lock time in FOL

mode is 398 cycles of divided reference clock when DPLL starts after full reset.

5 Tdck is the time period of the output clock, dpdck_2.

Table 34. NFC Clock Settings Examples

emi_slow_clk (MHz)

nfc_podf (Division Factor)

enfc_clk (MHz)

T-Clock Period (ns)

100 (Boot mode)

1 Boot value NFC_FREQ_SEL Fuse High (burned)

14.29

2 Boot value NFC_FREQ_SEL Fuse Low

33.33

133

33.33

344.333

3 For RBB_MODE=1, using NANDF_RB0 signal for ready/busy indication. This mode require setting the delay line. See the

Reference Manual for details.

22.5

2663

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