at83c5122 ATMEL Corporation, at83c5122 Datasheet - Page 48

• Manufacturer Part Number: at83c5122
• Description: At83c5123 C51 Microcontroller With Usb And Smart Card Reader Interfaces
• Manufacturer: ATMEL Corporation

SCIB Clock
48
AT8xC5122/23
The Smart Card Interface Block (SCIB) uses two clocks :
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.
External Clock
External Clock
48 MHz
24 MHz
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.
96 MHz
PLL
X1 mode selected
X2 mode selected
Prescaler
1/4
1/2
(Equivalent to)
(Equivalent to)
PERIPH frequency
PERIPH frequency
PERIPH frequency
CPU frequency
CPU frequency
CPU frequency
24 MHz
24 MHz
24 MHz
24 MHz
24 MHz
24 MHz
4202E–SCR–06/06