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Philips Semiconductors
User’s Manual - Preliminary -
P89LPC906/907/908
REAL-TIME CLOCK/SYSTEM TIMER
2003 Dec 8 48
Figure 6-1: Real-time clock/system timer Block Diagram
Table 6-1: Real-time Clock/System Timer Clock Source - P89LPC906
FOSC2
(UCFG1.2)
FOSC1
(UCFG1.1)
FOSC0
(UCFG1.0)
RTCS1:0
CCLK Frequency RTC Clock Frequency
000
00
High frequency crystal/DIVM
High frequency crystal
(XCLK)
01
10
11
High frequency crystal/DIVM
(CCLK)
001
00
Medium frequency crystal/DIVM
Medium frequency crystal
(XCLK)
01
10
11
Medium frequency crystal/
DIVM (CCLK)
010
00
Low frequency crystal/DIVM
Low frequency crystal
(XCLK)
01
10
11
Low frequency crystal/DIVM
(CCLK)
23-bit down counter
7-bit prescaler
RTCH RTCL
Interrupt
if enabled
(shared w. WDT)
Power-On
Reset
Low freq.
Med. freq.
High freq.
CCLK
XTAL1XTAL2
RTCEN
LSB
RTC underflow flag
ERTC
RTCF
RTCS1 RTCS2
RTC clk select
RTC Enable
Wake up from
Power-down
Int. Osc’s
MSB
÷ 128
RTC Reset
Reload on underflow