TS87C51RD2 ATMEL Corporation, TS87C51RD2 Datasheet - Page 13

• Manufacturer Part Number: TS87C51RD2
• Description: (TS8xC51Rx2) High Performance 8-bit Microcontroller
• Manufacturer: ATMEL Corporation

Figure 5-2.
4188E–8051–08/06
X T A L 1
X T A L 1 : 2
X 2 b i t
C P U c l o c k
Mode Switching Waveforms
S T D M o d e
Figure 5-1.
The X2 bit in the CKCON register
tion 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).
Note:
Table 5-2.
Bit Number
7
-
7
6
5
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 ref-
erence 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.
X T A L 1
Mnemonic
Clock Generation Diagram
CKCON Register
CKCON - Clock Control Register (8Fh)
6
Bit
F
-
-
-
-
X T A L
Description
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
2
X 2 M o d e
(Table
X T A L 1 : 2
4
-
5-2) allows to switch from 12 clock cycles per instruc-
C K C O N r e g
X 2
0
1
3
-
F
O S C
AT/TS8xC51Rx2
2
-
C P U c o n t r o l
s t a t e m a c h i n e : 6 c l o c k c y c l e s .
S T D M o d e
1
-
X2
0
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