DS_1215F_003
73S1215F Data Sheet
The master clock control register enables different sections of the clock circuitry and specifies the value
of the VCO Mcount divider. The MCLK must be configured to operate at 96MHz to ensure proper
operation of some of the peripheral blocks according to the following formula:
MCLK = (Mcount * 2 + 4) * FXTAL = 96MHz
Mcount is configured in the MCLKCtl register must be bound between a value of 1 to 7. The possible
crystal or external clock frequencies for getting MCLK = 96MHz are shown in Table 12.
Table 12: Frequencies and Mcount Values for MCLK = 96MHz
FXTAL (MHz)
12.00
9.60
Mcount (N)
2
3
4
5
6
8.00
6.86
6.00
Master Clock Control Register (MCLKCtl): 0x8F Å 0x0A
Table 13: The MCLKCtl Register
MSB
LSB
HSOEN KBEN SCEN USBEN 32KEN MCT.2 MCT.1 MCT.0
Bit
Symbol
Function
High-speed oscillator disable. When set = 1, disables the high-speed crystal
oscillator and VCO/PLL system. Do not set this bit = 1.
MCLKCtl.7
HSOEN
MCLKCtl.6
MCLKCtl.5
MCLKCtl.4
KBEN
SCEN
1 = Disable the keypad logic clock.
1 = Disable the smart card logic clock.
1 = Disable the USB logic clock.
USBEN
1 = Disable the 32Khz oscillator. When the 32kHz oscillator is enabled, the
RTC and other circuits such as debounce clocks are clocked using the
32kHz oscillator output. When disabled, the main oscillator provides the
32kHz clock for the RTC and other circuits. Note: This bit must be set if
there is no 32KHz crystal or the 44 pin package is used. Some internal
clocks and circuits will not run if the oscillator is enabled and no
crystal is connected.
MCLKCtl.3
32KEN
MCLKCtl.2
MCLKCtl.1
MCT.2
MCT.1
This value determines the ratio of the VCO frequency (MCLK) to the high-
speed crystal oscillator frequency such that:
MCLK = (MCount*2 + 4)* FXTAL. The default value is MCount = 2h such that
MCLK = (2*2 + 4)*12.00MHz = 96MHz.
MCLKCtl.0
MCT.0
The MPU clock that drives the CPU core defaults to 3.6923MHz after reset. The MPU clock is scalable
by configuring the MPU Clock Control register (MPUCKCtl).
Rev. 1.4
25
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
