LH79520 データシートの表示（PDF） - NXP Semiconductors.

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LH79520

System-on-Chip

NXP Semiconductors. 

System-on-Chip

NXP Semiconductors

LH79520

Real Time Clock

The RTC can provide a basic alarm function or long

time base counter. This is achieved by generating an

interrupt signal after counting for a programmed num-

ber of cycles of RTC input. Counting in one-second

intervals is achieved by the use of a 1 Hz clock input to

the RTC.

The features of the RTC are:

• 32-bit up counter with programmable load

• Programmable 32-bit match compare register

• Software maskable interrupt when counter and com-

pare registers are identical.

RTC input clock sources:

• PLL clock

• 32.768 kHz clock

• 1 Hz clock (default).

Watchdog Timer

The Watchdog Timer provides hardware protection

against malfunctions. It is a programmable timer to be

reset by software at regular intervals. Failure to reset

the timer will cause a FIQ interrupt. Failure to service

the FIQ interrupt will then generate a System Reset.

The features of the Watchdog Timer are:

• Driven by the bus clock

• 16 programmable time-out periods: 216 through 231

clock cycles

• Generates a system reset (resets LH79520) or a FIQ

Interrupt whenever a time-out period is reached

• Software enable, lockout, and counter-reset mecha-

nisms add security against inadvertent writes

• Protection mechanism guards against interrupt-ser-

vice failure:

– The first WDT time-out triggers FIQ and asserts

nWDFIQ status flag

– If FIQ service routine fails to clear nWDFIQ, then

the next WDT time-out triggers a soft reset.

Timer

The LH79520 incorporates two Timer modules,

each comprising two 16-bit independently programma-

ble timers. This gives a total of four independent timers.

• Each timer has two operating modes:

– Free-running mode: After reaching 0x0000 the

timer wraps around to 0xFFFF and generates an

interrupt request. It continues to count down from

0xFFFF.

– Periodic timer mode: After reaching 0x0000 the

timer is automatically reloaded with its pro-

grammed value and generates an interrupt re-

quest. It continues to count down from the

loaded value.

• Each timer contains a programmable pre-scaler:

– Bus clock divided by 1, 16, or 256

• Timers can be cascaded to achieve longer timing

periods

• Carry-out of higher-order timer provides clock signal

for next lower order timer

• Possible timing ranges:

– 215 (single timer)

– 231 (two timers cascaded)

– 247 (three timers cascaded)

– 263 (four timers cascaded)

• Output signal of lowest order timer is externally avail-

able as CTOUT1B signal.

Input/Output Configuration System

The registers provided by the IOCON System allow

the user to directly control the pin multiplexing of the

device; by setting or clearing bits in a set of registers, the

user can configure the LH79520 for peripheral devices.

General Purpose Input/Output (GPIO)

The LH79520 provides up to 64 bits of programma-

ble input/output. These eight 8-bit ports are Ports A

through H, and are multiplexed with other signals.

• Individually programmable input/output pins

• All I/O ports default to Input on power-up.

Preliminary data sheet

Rev. 01 — 16 July 2007

21

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