Rainbow Electronics AT89C5122 - Manual (Page 78)

78
AT8xC5122/23
4202E–SCR–06/06
Alternate Card A second card named ‘Alternate Card’ can be controlled.
The Clock signal CCLK1 can be adapted to the XTAL frequency. Thanks to the clock
prescaler which can divide the frequency by 1, 2, 4 or 8. The bits ALTKPS0 and
ALTKPS1 in SCSR Register are used to set this factor.
Figure 45. Alternate Card
Registers
There are fifteen registers to control the SCIB macro-cell. They are described from
Table 58 to Table 45.
Some of the register widths are greater than a byte. Despite the 8 bits access provided
by the BIU, the address mapping of this kind of register respects the following rule :
The Low significant byte register is implemented at the higher address.
This implementation makes access to these registers easier when using high level pro-
gramming languages (C,C++).
SIM, SAM
CARD
Alternate
card
CVCC
CRST
CIO
CCLK
CK_IDLE
1
0
CCLK1
SCSR Reg.
PR3
SCCLK1
1, 1/2, 1/4 or 1/8
P1.7
Main
card
CPRES
SMART
CARD
SCSR Reg.
ALTKPS0,1