Interrupt controller, Real-time clock, Pll and clocking – Cirrus Logic EP7312 User Manual
Page 9
DS508F2
Copyright Cirrus Logic, Inc. 2011
(All Rights Reserved)
9
EP7312
High-Performance, Low-Power System on Chip
strobes for each keyboard column signal. The pins of Port A,
when configured as inputs, can be selectively OR'ed together
to provide a keyboard interrupt that is capable of waking the
system from a STANDBY or IDLE state. The Keypad
Interface has these features:
•
Column outputs can be individually set high with the
remaining bits left at high-impedance
•
Column outputs can be driven all-low, all-high, or all-high-
impedance
•
Keyboard interrupt driven by OR'ing together all Port A
bits
•
Keyboard interrupt can be used to wake up the system
•
8
8 keyboard matrix usable with no external logic, extra
keys can be added with minimal glue logic
shows the Keypad Interface Pin Assignments.
Interrupt Controller
When unexpected events arise during the execution of a
program (i.e., interrupt or memory fault) an exception is
usually generated. When these exceptions occur at the same
time, a fixed priority system determines the order in which
they are handled. The EP7312 interrupt controller has two
interrupt types: interrupt request (IRQ) and fast interrupt
request (FIQ). The interrupt controller has the ability to control
interrupts from 22 different FIQ and IRQ sources. The
Interrupt controller has these features:
•
Supports 22 interrupts from a variety of sources (such as
UARTs, SSI1, and key matrix.)
•
Routes interrupt sources to the ARM720T’s IRQ or FIQ
(Fast IRQ) inputs
•
Five dedicated off-chip interrupt lines operate as level
sensitive interrupts
shows the interrupt controller pin assignments.
.
Note:
Pins are multiplexed. See
for
more information.
Real-Time Clock
The EP7312 contains a 32-bit Real Time Clock (RTC) that can
be written to and read from in the same manner as the timer
counters. It also contains a 32-bit output match register which
can be programmed to generate an interrupt.
•
Driven by an external 32.768 kHz crystal oscillator
shows the Real-Time Clock pin assignments.
PLL and Clocking
The EP7312 processor and peripheral clocks have these
features:
•
Processor and peripheral clocks operate from a single
3.6864 MHz crystal or external 13 MHz clock
•
Programmable clock speeds allow the peripheral bus to run
at 18 MHz when the processor is set to 18 MHz and at
36 MHz when the processor is set to 36, 49 or 74 MHz, and
at 45 MHz when the processor is set to 90 MHz.
shows the PLL and clocking pin assignments.
Table 10. Keypad Interface Pin Assignments
Pin Mnemonic
I/O
Pin Description
COL[7:0]
O
Keyboard scanner column
drive
Table 11. Interrupt Controller Pin Assignments
Pin Mnemonic
I/O
Pin Description
nEINT[2:1]
I
External interrupt
EINT[3]
I
External interrupt
nEXTFIQ
I
External Fast Interrupt input
nMEDCHG/nBROM
(Note)
I
Media change interrupt input
Table 12. Real-Time Clock Pin Assignments
Pin Mnemonic
Pin Description
RTCIN
Real-Time Clock Oscillator Input
RTCOUT
Real-Time Clock Oscillator Output
VDDRTC
Real-Time Clock Oscillator Power
VSSRTC
Real-Time Clock Oscillator Ground
Table 13. PLL and Clocking Pin Assignments
Pin Mnemonic
Pin Description
MOSCIN
Main Oscillator Input
MOSCOUT
Main Oscillator Output
VDDOSC
Main Oscillator Power
VSSOSC
Main Oscillator Ground