Rainbow Electronics AT83C26 - Manual (Page 51)

51
7511B–SCR–10/05
AT83C26
Reset value = 0x 0X00 1000
Notes: 1. When CKS4 value is changed a special logic insures no glitch occurs on the CCLK4 pin and
actual configuration changes can be delayed by half a period to two periods of CCLK4.
2. CCLK4 must be stopped with CKSTOP4 bit before switching from CKS4 = (0, 1, 2, 3, 6, 7) to
CKS4 = (4, 5) or vice versa.
Table 30. SC4_CFG2 ()
7 6 5 4 3 2 1 0
ART4 X CARDRST4 CARDCK4 CKSTOP4 CKS42 CKS41 CKS40
Bit Number Bit Mnemonic Description
7 ART4
Automatic Reset Transition
Set this bit to have the CRST4 pin changed according to activation sequence.
Clear this bit to have the CRST4 pin immediately following the value programmed in CARDRST4.
6 X
5 CARDRST4
Card Reset
Set this bit to enter a reset sequence according to ART4 bit value.
Clear this bit to drive a low level on the CRST4 pin.
4 CARDCK4
Card Clock
Set this bit to set a high level on the CCLK4 pin (according to CKSTOP4 bit value).
Clear this bit to drive a low level on the CCLK4 pin.
3 CKSTOP4
CARD Clock Stop
Set this bit to stop CCLK4 according to CARDCK4. This can be used to set asynchronous cards in power-
down mode (GSM) or to drive CCLK4 by software.
Clear this bit to have CCLK4 running according to CKS4. This can be used to activate asynchronous cards.
Note: When this bit is changed a special logic ensures that no glitch occurs on the CCLK4 pin and actual
configuration changes can be delayed by half a period to two periods of CCLK4.
2-0 CKS4[2:0]
Interface 4Card Clock Selection
CKS4 [2:0] = 0: CCLK4 = CLK (then the maximum frequency is 24 MHz)
CKS4 [3:0] = 1: CCLK4 = DCCLK
CKS4 [3:0] = 2: CCLK4 = DCCLK / 2
CKS4 [3:0] = 3: CCLK4 = DCCLK / 4
CKS4 [3:0] = 4: CCLK4 = A2
CKS4 [3:0] = 5: CCLK4 = A2 / 2
CKS4 [3:0] = 6: CCLK4 = CLK / 2
CKS4 [3:0] = 7: CCLK4 = CLK / 4
The reset value is 0.