AT89C51RD2-RDTIM Atmel, AT89C51RD2-RDTIM Datasheet - Page 19

• Manufacturer Part Number: AT89C51RD2-RDTIM
• Description: MCU 8-Bit AT89 80C51 CISC 64KB Flash 3.3V/5V 64-Pin VQFP Tray
• Manufacturer: Atmel

4235J–8051–01/08
Reset Value = 0000 000’HSB. X2’b (See “Hardware Security Byte”)
Not bit addressable
Table 7-2.
CKCON1 - Clock Control Register (AFh)
Number
Number
Bit
Bit
5
4
3
2
1
0
7
6
5
4
3
7
-
Mnemonic
Mnemonic
CKCON1 Register
PCAX2
T2X2
T1X2
T0X2
SIX2
Bit
Bit
X2
6
-
-
-
-
-
-
Description
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 6 clock 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.
Description
Reserved
Reserved
Reserved
Reserved
Reserved
5
-
4
-
3
-
AT89C51RD2/ED2
2
-
1
-
SPIX2
0
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