LH79520_N NXP Semiconductors, LH79520_N Datasheet - Page 21

• Manufacturer Part Number: LH79520_N
• Description: The LH79520, powered by an ARM720T, is a completeSystem-on-Chip with a high level of integration tosatisfy a wide range of requirements and expectations
• Manufacturer: NXP Semiconductors

System-on-Chip
Real Time Clock
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.
• 32-bit up counter with programmable load
• Programmable 32-bit match compare register
• Software maskable interrupt when counter and com-
• PLL clock
• 32.768 kHz clock
• 1 Hz clock (default).
Watchdog Timer
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: 2
• Generates a system reset (resets LH79520) or a FIQ
• Software enable, lockout, and counter-reset mecha-
• Protection mechanism guards against interrupt-ser-
Preliminary data sheet
pare registers are identical.
clock cycles
Interrupt whenever a time-out period is reached
nisms add security against inadvertent writes
vice failure:
The RTC can provide a basic alarm function or long
The features of the RTC are:
RTC input clock sources:
The Watchdog Timer provides hardware protection
– The first WDT time-out triggers FIQ and asserts
– If FIQ service routine fails to clear nWDFIQ, then
nWDFIQ status flag
the next WDT time-out triggers a soft reset.
16
through 2
Rev. 01 — 16 July 2007
NXP Semiconductors
31
Timer
each comprising two 16-bit independently programma-
ble timers. This gives a total of four independent timers.
• Each timer has two operating modes:
• Each timer contains a programmable pre-scaler:
• Timers can be cascaded to achieve longer timing
• Carry-out of higher-order timer provides clock signal
• Possible timing ranges:
• Output signal of lowest order timer is externally avail-
Input/Output Configuration System
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)
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.
periods
for next lower order timer
able as CTOUT1B signal.
The LH79520 incorporates two Timer modules,
– Free-running mode: After reaching 0x0000 the
– Periodic timer mode: After reaching 0x0000 the
– Bus clock divided by 1, 16, or 256
– 2
– 2
– 2
– 2
The registers provided by the IOCON System allow
The LH79520 provides up to 64 bits of programma-
timer wraps around to 0xFFFF and generates an
interrupt request. It continues to count down from
0xFFFF.
timer is automatically reloaded with its pro-
grammed value and generates an interrupt re-
quest. It continues to count down from the
loaded value.
15
31
47
63
(single timer)
(two timers cascaded)
(three timers cascaded)
(four timers cascaded)
LH79520
21