CY28435 Cypress Semiconductor, CY28435 Datasheet - Page 10

• Manufacturer Part Number: CY28435
• Description: Clock Generator
• Manufacturer: Cypress Semiconductor

Document #: 38-07664 Rev. *B
Byte 14: Control Register 14 (continued)
Byte 15: Control Register 15
Byte 16: Control Register 16
Crystal Recommendations
The CY28435 requires a Parallel Resonance Crystal. Substi-
tuting a series resonance crystal will cause the CY28435 to
operate at the wrong frequency and violate the ppm specifi-
cation. For most applications there is a 300-ppm frequency
shift between series and parallel crystals due to incorrect
loading.
Bit
Bit
Bit
4
3
2
1
0
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
@Pup
@Pup
@Pup
0
0
0
1
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
1
Watchdog Autorecovery Watchdog Autorecovery Mode
SRC_FREQ_SEL
Prog_SRC_EN
Prog_CPU_EN
Recovery_N8
Recovery N7
Recovery N6
Recovery N5
Recovery N4
Recovery N3
Recovery N2
Recovery N1
Recovery N0
SMSW_SEL
RESERVED
RESERVED
RESERVED
SRC_SATA
USB48_1
Name
Name
Name
REF1
PCIF
PRELIMINARY
Smooth switch select
0: select CPU_PLL
1: select SRC_PLL.
RESERVED, Set = 0
RESERVED, Set = 0
Free running 33-MHz Output Drive Strength
0 = 2x, 1 = 1x
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
REF1 Output Enable
0 = Disable, 1 = Enable
USB48_1 Output Enable
0 = Disable, 1 = Enable
SRC Frequency selection
0: SRC frequency is selected via the FSE pin
1: SRC frequency is initially set to 167MHz.
RESERVED, Set = 0
SATA PLL Spread Spectrum Enable
0 = Spread off, 1 = Spread on
Programmable SRC frequency enable
0 = disabled, 1 = enabled.
Programmable CPU frequency enable
0 = disabled, 1 = enabled.
0 = Disable (Manual), 1= Enable (Auto)
Crystal Loading
Crystal loading plays a critical role in achieving low ppm perfor-
mance. To realize low ppm performance, the total capacitance
the crystal will see must be considered to calculate the appro-
priate capacitive loading (CL).
Figure 2 shows a typical crystal configuration using the two
trim capacitors. An important clarification for the following
discussion is that the trim capacitors are in series with the
crystal not parallel. It’s a common misconception that load
capacitors are in parallel with the crystal and should be
approximately equal to the load capacitance of the crystal.
This is not true.
Description
Description
Description
CY28435
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