CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
85
9. Internal Low Speed Oscillator (ILO)
This chapter briefly explains the Internal Low Speed Oscillator (ILO) and its associated register. The Internal Low Speed
Oscillator produces a 32 kHz clock. For a quick reference of all PSoC
®
registers in address order, refer to the
.
9.1
Architectural Description
The Internal Low Speed Oscillator (ILO) is an oscillator with
a nominal frequency of 32 kHz. It is used to generate Sleep
Wakeup interrupts and watchdog resets. This oscillator can
also be used as a clocking source for the digital PSoC
blocks.
The oscillator operates in three modes: normal power, low
power, and off. The Normal Power mode consumes more
current to produce a more accurate frequency. The Low
Power mode is always used when the part is in a power
down (sleep) state.
9.2
Register Definitions
The following register is associated with the Internal Low Speed Oscillator (ILO). The register description has an associated
register table showing the bit structure. The bits in the table that are grayed out are reserved bits and are not detailed in the
register description that follows. Note that reserved bits should always be written with a value of ‘0’.
9.2.1
ILO_TR Register
The Internal Low Speed Oscillator Trim Register (ILO_TR)
sets the adjustment for the internal low speed oscillator.
The device specific value, placed in the trim bits of this reg-
ister at boot time, is based on factory testing.
It is strongly
recommended that the user not alter the values in the
register
.
Bits 5 and 4: Bias Trim[1:0].
These two bits are used to
set the bias current in the PTAT Current Source. Bit 5 gets
inverted, so that a medium bias is selected when both bits
are ‘0’. The
is set according to
Bits 3 to 0: Freq Trim[3:0].
These four bits are used to
trim the frequency. Bit 0 is the LSb and bit 3 is the MSb. Bit 3
gets inverted inside the register.
For additional information, refer to the
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,E9h
Bias Trim[1:0]
Freq Trim[3:0]
RW : 00
Table 9-1. Bias Current in PTAT
Bias Current
Bias Trim [1:0]
Medium Bias
00b
Maximum Bias
01b
Minimum Bias
10b
Reserved 11b
Summary of Contents for CY8C28 series
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