ADUC7021 Analog Devices, ADUC7021 Datasheet - Page 79

• Manufacturer Part Number: ADUC7021
• Manufacturer: Analog Devices

Specifications of ADUC7021

• Mcu Core: ARM7 TDMI
• Mcu Speed (mips): 40
• Sram (bytes): 8192Bytes
• Gpio Pins: 13
• Adc # Channels: 8

FIQ
The fast interrupt request (FIQ) is the exception signal to enter
the FIQ mode of the processor. It is provided to service data
transfer or communication channel tasks with low latency. The
FIQ interface is identical to the IRQ interface providing the
second-level interrupt (highest priority). Four 32-bit registers
are dedicated to FIQ: FIQSIG, FIQEN, FIQCLR, and FIQSTA.
Table 163. FIQSTA Register
Name
FIQSTA
Table 164. FIQSIG Register
Name
FIQSIG
1
Table 165. FIQEN Register
Name
FIQEN
Table 166. FIQCLR Register
Name
FIQCLR
Bit 31 to Bit 1 of FIQSTA are logically OR’ d to create the FIQ
signal to the core and to Bit 0 of both the FIQ and IRQ registers
(FIQ source).
The logic for FIQEN and IRQEN does not allow an interrupt
source to be enabled in both IRQ and FIQ masks. A bit set to 1
in FIQEN does, as a side effect, clear the same bit in IRQEN.
Also, a bit set to 1 in IRQEN does, as a side effect, clear the
same bit in FIQEN. An interrupt source can be disabled in both
the IRQEN and FIQEN masks.
Note that to clear an already enabled FIQ source, the user must
set the appropriate bit in the FIQCLR register. Clearing an
interrupt’s FIQEN bit does not disable the interrupt.
Programmed Interrupts
Because the programmed interrupts are nonmaskable, they are
controlled by another register, SWICFG, which simultaneously
writes into the IRQSTA and IRQSIG registers and/or the
FIQSTA and FIQSIG registers. The 32-bit SWICFG register is
dedicated to software interrupts(see Table 168). This MMR
allows the control of a programmed source interrupt.
Table 167. SWICFG Register
Name
SWICFG
X indicates an undefined value.
Address
0xFFFF0100
Address
0xFFFF0104
Address
0xFFFF0108
Address
0xFFFF010C
Address
0xFFFF0010
Default Value
0x00000000
Default Value
0x00XXX000
Default Value
0x00000000
Default Value
0x00000000
Default Value
0x00000000
1
Access
R
Access
R
Access
R/W
Access
W
Access
W
Rev. D | Page 79 of 96
Table 168. SWICFG MMR Bit Descriptions
Bit
31:3
2
1
0
Note that any interrupt signal must be active for at least the
equivalent of the interrupt latency time, which is detected by
the interrupt controller and by the user in the IRQSTA/FIQSTA
register.
TIMERS
The ADuC7019/20/21/22/24/25/26/27/28/29 have four general-
purpose timer/counters.
•
•
•
•
These four timers in their normal mode of operation can be
either free running or periodic.
In free-running mode, the counter decreases from the
maximum value until zero scale and starts again at the
minimum value. (It also increases from the minimum value
until full scale and starts again at the maximum value.)
In periodic mode, the counter decrements/increments from the
value in the load register (TxLD MMR) until zero/full scale and
starts again at the value stored in the load register.
The timer interval is calculated as follows:
The value of a counter can be read at any time by accessing its
value register (TxVAL). Note that when a timer is being clocked
from a clock other than core clock, an incorrect value may be
read (due to an asynchronous clock system). In this configur-
ation, TxVAL should always be read twice. If the two readings
are different, it should be read a third time to get the correct
value.
Timers are started by writing in the control register of the
corresponding timer (TxCON).
In normal mode, an IRQ is generated each time the value of the
counter reaches zero when counting down. It is also generated
each time the counter value reaches full scale when counting
up. An IRQ can be cleared by writing any value to clear the
register of that particular timer (TxCLRI).
ADuC7019/20/21/22/24/25/26/27/28/29
Timer0
Timer1
Timer2 or wake-up timer
Timer3 or watchdog timer
Interval
Reserved.
Description
Programmed interrupt (FIQ). Setting/clearing this bit
corresponds with setting/clearing Bit 1 of FIQSTA
and FIQSIG.
Programmed interrupt (IRQ). Setting/clearing this bit
corresponds with setting/clearing Bit 1 of IRQSTA
and IRQSIG.
Reserved.
=
(
TxD
Source
)
×
Prescaler
Clock