at89c51ic2-slsim ATMEL Corporation, at89c51ic2-slsim Datasheet - Page 23

• Manufacturer Part Number: at89c51ic2-slsim
• Description: At89c51ic2 8-bit Flash Microcontroller With 2-wire Interface
• Manufacturer: ATMEL Corporation

4301D–8051–02/08
Table 19. CKCON0 Register
CKCON0 - Clock Control Register (8Fh)
Reset Value = 0000 000’HSB.X2’b
Not bit addressable
Number
SPIX2
Bit
7
7
6
5
4
3
2
1
0
Mnemonic
WDX2
PCAX2
WDX2
I2CX2
T2X2
T1X2
T0X2
SIX2
Bit
6
X2
Description
2-wire clock (This control bit is validated when the CPU clock X2 is set; when
X2 is low, this bit has no effect)
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
Watchdog clock (This control bit is validated when the CPU clock X2 is set;
when X2 is low, this bit has no effect)
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
Programmable Counter Array clock (This control bit is validated when the
CPU clock X2 is set; when X2 is low, this bit has no effect)
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
Enhanced UART clock (Mode 0 and 2) (This control bit is validated when the
CPU clock X2 is set; when X2 is low, this bit has no effect)
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
Timer2 clock (This control bit is validated when the CPU clock X2 is set; when
X2 is low, this bit has no effect)
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
Timer1 clock (This control bit is validated when the CPU clock X2 is set; when
X2 is low, this bit has no effect)
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
Timer0 clock (This control bit is validated when the CPU clock X2 is set; when
X2 is low, this bit has no effect)
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
CPU clock
Cleared to select 12 clock periods per machine cycle (STD mode) for CPU and
all the peripherals.
Set to select 6clock periods per machine cycle (X2 mode) and to enable the
individual peripherals "X2" bits.
Programmed by hardware after Power-up regarding Hardware Security Byte
(HSB), Default setting, X2 is cleared.
PCAX2
5
SIX2
4
T2X2
3
T1X2
2
T0X2
1
X2
0
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