at83c5122 ATMEL Corporation, at83c5122 Datasheet - Page 74

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

Additional Features
Clock
Card Presence Input
74
XTAL1 (MHz)
8
8
8
8
8
8
AT8xC5122/23
EXT48
0
0
0
0
0
0
The CK_ISO input must be in the range 1 - 5 MHz according to ISO 7816.
The CK_ISO can be programmed up to 12 MHz. In this case, the timing specification of
the output buffer will not comply to ISO 7816.
Figure 41. Clock Diagram of the SCIB Block
Figure 42. Prescaler 2 Description
The division factor SCICLK must be smaller than 49. If it is greater or equal to 49, the
PR2 prescaler is locked.
See Figure 17 clock tree diagram in the clock controller chapter.
Table 42. Examples of Clock settings
The internal pull-up (weak pull-up) on Card Presence input can be disconnected in order
to reduce the consumption (CPRESRES, bit 3 in PMOD0).
In this case, an external resistor (typically 1 M ) must be externally tied to Vcc.
CPRES input can generate an interrupt (see Interrupt system section).
The detection level can be selected.
XTSCS
PLLCON.2
SCICLK.7
EXT48
CK_IDLE
CK_PLL or
CK_XTAL1
CK_PLL
CK_XTAL1
SCICLK
36
44
42
40
24
0
0
1
PR2
1/(2*(48 - SCICLK[5-0]))
PR2
Ck_cpu
Ck_ISO
SCIB
SCICLK[5:0]
CK_ ISO
=48
<48
12
4
8
6
2
1
CK_ISO
4202E–SCR–06/06