Rainbow-electronics AT89C5122 Bedienungsanleitung PDF herunterladen (Seite 50)

AT8xC5122/23

4202E–SCR–06/06

USB Interface Clock The USB Interface uses two clocks :

– The first one is the CPU clock used for the interface with the microcontroller,

CK_IDLE.

– The second one is the CK_USB supplied from the PLL through a divider by

Registers

Reset Value = XXXX XXX0b

Reset Value = XXXX 1111b

Table 24. Clock Selection Register - CKSEL (S:85h)

76543210

-------CKS

Bit Number Bit Mnemonic Description

7:1 -

Reserved

The value read from this bit is indeterminate. Do not set this bit.

0CKS

CPU Oscillator Select Bit

Set this bit to connect CPU and Peripherals to PLL output.

Clear this to to connect CPU and Peripherals to XTAL1 clock input.

Table 25. Clock Reload Register - CKRL (S:97h)

76543210

- - - - CKRL3 CKRL2 CKRL1 CKRL0

Bit Number Bit Mnemonic Description

7 - 4 -

Reserved

The value read from this bit is indeterminate. Do not set this bit.

3:0 CKRL3:0

Clock Reload register

Prescaler1 value

ck_cpu

=[ 1 / 2*(16-CKRL)] * F

ck_XTAL1

1 2 ... 45 46 47 48 49 50 51 52 53 54 55 ... 212 213

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Rainbow-electronics AT89C5122 Bedienungsanleitung Seite 50