Rainbow-electronics AT89C5122 Manual do Utilizador descarregar pdf (Página 48)

AT8xC5122/23

4202E–SCR–06/06

SCIB Clock The Smart Card Interface Block (SCIB) uses two clocks :

– The first one, CK_IDLE, is the peripheral clock used for the interface with the

microcontroller.

– The second one, CK_ISO, is independant from the CPU clock and is

generated from the PLL or XTAL1 output.

PR2, a 6-bit prescaler, will be used to generate:

12/9.6/8/6.85/6/5.33/4.8/4.36/ ..../1MHz frequencies.

SCIB clock frequency must be lower than CPU clock frequency.

During SCIB Reset, the CK_ISO input must be in the range 1 - 5 MHz according to ISO

7816. The SCIB clocks frequency is defined in Figure 42 on page 74 and Table 42 on

page 74.

Two conditions must be met for a correct use of the SCIB:

• CK_CPU > 4/3 * CK_ISO and

• CK_CPU < 6 * CK_ISO.

96 MHz

CPU frequency

24 MHz

PLL

1/4

Prescaler

48 MHz

1/2

External Clock CPU frequency

24 MHz

(Equivalent to)

X1 mode selected

24 MHz

CPU frequency

24 MHz

(Equivalent to)

X2 mode selected

PERIPH frequency

24 MHz

PERIPH frequency

24 MHz

PERIPH frequency

24 MHz

External Clock

1 2 ... 43 44 45 46 47 48 49 50 51 52 53 ... 212 213

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Rainbow-electronics AT89C5122 Manual do Utilizador Página 48