xe8802 Semtech Corporation, xe8802 Datasheet - Page 49

• Manufacturer Part Number: xe8802
• Description: Data Acquisition Soc With 16+10 Bit Zoomingadc? Embedded Risc Controller And Lcd Driver
• Manufacturer: Semtech Corporation

7.1
3 available clock sources (RC oscillator, quartz oscillator and external clock).
•
•
7.2
The XE88LCxx chips can work on different clock sources (RC oscillator, quartz oscillator and external clock). The
clock generator block is in charge of distributing the necessary clock frequencies to the circuit.
Figure 7-1 represents the functionality of the clock block.
The internal RC oscillator or an external clock source can be selected to drive the high prescaler. This prescaler
generates frequency divisions down to 1/256 of its input frequency. A 32kHz clock is generated by enabling the
quartz oscillator (if present in the product) or by selecting the appropriate tap on the high prescaler. The low
prescaler generates clock signals from 32kHz down to 1Hz. The clock source for the CPU can be selected from the
RC oscillator, the external clock or the 32kHz clock.
7.3
© Semtech 2006
2 divider chains: high-prescaler (8 bits) and low-prescaler (15 bits).
CPU clock disabling in halt mode.
Features
Overview
Register map
7
6
5
4
3
2
1
0
7-2
1
0
7-1
0
pos.
pos.
pos.
CpuSel
-
EnExtClock
BiasRc
ColdXtal
-
EnableXtal
EnableRc
--
Output16k
OutputCpuCk
--
ClearLowPrescal
RegSysClock
RegSysMisc
RegSysPre0
r/w
r
r/w
r/w
r
r
r/w
r/w
r
r/w
r/w
r
w1
r0
rw
rw
rw
Table 7-1: RegSysClock register
Table 7-2: RegSysMisc register
Table 7-3: RegSysPre0 register
XE8802 Sensing Machine Data Acquisition MCU
0 nresetsleep
0
0 nresetcold
1 nresetcold
1 nresetsleep
0
0 nresetsleep
1 nresetsleep
000000
0000000
0
0 nresetsleep
0 nresetsleep
reset
reset
reset
7-2
with ZoomingADC™ and LCD driver
Select speed for cpuck
Unused
Enable for external clock
Enable Rcbias (reduces start-up time of RC).
Xtal in start phase
Unused
Enable Xtal oscillator
Enable RC oscillator
Unused
Output 16 kHz signal on PB[3]
Output CPU clock on PB[2]
Unused
Write 1 to reset low prescaler, but always
reads 0
function
function
function
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