LM8322JGR8 NSC [National Semiconductor], LM8322JGR8 Datasheet - Page 8

• Manufacturer Part Number: LM8322JGR8
• Description: Mobile I/O Companion Supporting Key-Scan, I/O Expansion, PWM, and ACCESS.bus Host Interface
• Manufacturer: NSC [National Semiconductor]

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9.0 Clocks
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9.1 INTERNAL EXECUTION CYCLE
The Processing - and Command - execution clock is about 2
MHz. This clock is stopped in Halt mode, which only occurs
under control of the LM8322. However, the host can set the
period of inactivity which causes the device to enter Halt
mode.
Exit from Halt mode can be triggered by any of these events:
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After reset, the default timebase for the PWM outputs is the
internal execution clock divided by 64.
System Clock (mclk) — The system clock is in the range
of about 21 MHz (± 7%) typical. This clock is used to drive
the I
clock for other function blocks.
Processing and Command Execution Clock (t
internal processing is based on a 2 MHz clock. This clock
is derived from the System Clock.
Internal PWM Clock — The internal PWM clock is a fixed
scaled down clock (÷ 64) of the Processing and Command
Occurrence of a key-press or key-release event.
A Start condition driven by the host on the ACCESS.bus
interface.
Assertion of the RESET input.
2
C compatible serial ACCESS bus and is the input
FIGURE 2. Clock Architecture
C
) — The
8
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9.2 BUFFERED CLOCK
The timebase for the PWM comes from any of three sources:
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Any of these sources may be buffered and driven on the
SLOWCLKOUT output. The clock buffer is enabled with the
WRITE_CLOCK command.
If XTAL_IN is not used it must be terminated to V
Execution Clock. This clock is close to 32 kHz which is in
a good range to source the PWM function block as an
alternative to an external clock source.
External 32.768 kHz Clock — driven into the SLOWCLK
input. May be used internally as the timebase for the PWM
and driven on the SLOWCLKOUT output.
External 32.768 kHz Crystal — connected across the
XTAL_IN and XTAL_OUT pins (XTAL_IN is an alternate
function of the SLOWCLK pin). May be used internally as
the timebase for the PWM and driven on the
SLOWCLKOUT output.
Prescaled internal Execution clock.
External 32.768 kHz clock received on the SLOWCLK
input.
On-chip oscillator with an external crystal connected
across XTAL_IN and XTAL_OUT.
30013602
CC
or GND.