eorex
EU1010
Base Timer
Base timer is optioned from [BASE1, BASE0] and it will cause a period timer base interrupt enabled
(TBINT=1) & (TBEN=1).
BASE1
BASE0
TBASE
TT/2
0
0
1
1
0
1
0
1
TT/4
TT/8
TT/16
MCU clock selection
With a built-in internal RC oscillator, the MCU frequency (Fosc) is 4MHz ±3% @4.5V. MCU system
clock (Fsys) offers 4MHz, 2MHz, 1MHz, 500KHz or 250KHz by MCU clock options bit; RCSEL2~0.
Please refer to the following table.
Address
Name
03H
bit7
#
bit6
bit5
bit4
bit3
bit2
bit1
bit0
UCCLK
BASE1 BASE0 RTC1 RTC0 RCSEL2RCSEL1RCSEL0
Read or Write
Default Value
#
W
0
W
0
W
0
W
0
W
0
W
0
W
0
0
The MCU system clock could be switched by setting RCSEL2~0. First, pre-set RCSEL2~0 register and
then execute “HALT” instruction. After then, MCU wake-up from HALT mode, MCU system frequency is
already changed to the new setting frequency.
RCSEL2
RCSEL1
RCSEL0
Frequency of MCU system clock (Fsys)
0
0
0
0
1
0
0
1
1
#
0
1
0
1
#
250KHz
500KHz
1MHz
2MHz
4MHz (Fosc)
Feb.2009
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EOREX [ EOREX CORPORATION ]
