TS87C51RC2 ATMEL Corporation, TS87C51RC2 Datasheet - Page 12

• Manufacturer Part Number: TS87C51RC2
• Description: High Performance 8-bit Microcontroller 32 Kbytes Otp
• Manufacturer: ATMEL Corporation

TS80C51RA2/RD2
TS83C51RB2/RC2/RD2
TS87C51RB2/RC2/RD2
The X2 bit in the CKCON register (See Table 3.) allows to switch from 12 clock cycles per instruction to 6 clock
cycles and vice versa. At reset, the standard speed is activated (STD mode). Setting this bit activates the X2 feature
(X2 mode).
CAUTION
In order to prevent any incorrect operation while operating in X2 mode, user must be aware that all peripherals
using clock frequency as time reference (UART, timers, PCA...) will have their time reference divided by two.
For example a free running timer generating an interrupt every 20 ms will then generate an interrupt every 10 ms.
UART with 4800 baud rate will have 9600 baud rate.
12
XTAL1
XTAL1:2
X2 bit
CPU clock
STD Mode
Figure 2. Mode Switching Waveforms
X2 Mode
Rev. C - 06 March, 2001
STD Mode