AT80C51RD2 Atmel Corporation, AT80C51RD2 Datasheet - Page 10

• Manufacturer Part Number: AT80C51RD2
• Manufacturer: Atmel Corporation

Specifications of AT80C51RD2

• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Sram (kbytes): 1.25
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Watchdog: Yes

Figure 6-2.
10
AT80C51RD2
XTAL1
XTAL1:2
X2 Bit
CPU Block
Mode Switching Waveforms
STD Mode
The X2 bit in the CKCON0 register (see Table 6-1) allows to switch from 12 clock periods per
instruction to 6 clock periods and vice versa. At reset, the speed is set according to X2 bit of
Hardware Config Byte (HCB). By default, Standard mode is activated. Setting the X2 bit acti-
vates the X2 feature (X2 mode).
The T0X2, T1X2, T2X2, UARTX2, PCAX2 and WDX2 bits in the CKCON0 register
allow to switch from standard peripheral speed (12 clock periods per peripheral clock cycle) to
fast peripheral speed (6 clock periods per peripheral clock cycle). These bits are active only in
X2 mode.
Table 6-1.
CKCON0 - Clock Control Register (8Fh)
Number
Bit
7
6
7
-
Mnemonic
CKCON0 Register
WDX2
WDX2
Bit
6
-
Description
Reserved
Do not set this bit.
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.
PCAX2
5
F
OSC
X2 Mode
SIX2
4
T2X2
3
T1X2
2
STD Mode
T0X2
1
4113D–8051–01/09
(Table
X2
0
6-1)