參數(shù)資料
型號(hào): COP8SBR9KMT8
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類: 微控制器/微處理器
英文描述: 8-Bit CMOS Flash Based Microcontroller with 32k Memory, Virtual EEPROM and Brownout
中文描述: 8-BIT, FLASH, 20 MHz, MICROCONTROLLER, PDSO56
封裝: TSSOP-56
文件頁數(shù): 22/80頁
文件大?。?/td> 972K
代理商: COP8SBR9KMT8
10.0 Functional Description
(Continued)
RANDOM after RESET at power-on
T2CNTRL: CLEARED
T3CNTRL: CLEARED
HSTCR: CLEARED
ITMR: Cleared except Bit 6 (HSON) = 1
Accumulator, Timer 1, Timer 2 and Timer 3:
RANDOM after RESET
WKEN, WKEDG: CLEARED
WKPND: RANDOM
SP (Stack Pointer):
Initialized to RAM address 06F Hex
B and X Pointers:
UNAFFECTED after RESET with power already applied
RANDOM after RESET at power-on
S Register: CLEARED
RAM:
UNAFFECTED after RESET with power already applied
RANDOM after RESET at power-on
USART:
PSR, ENU, ENUR, ENUI: Cleared except the TBMT bit
which is set to one.
ISP CONTROL:
ISPADLO: CLEARED
ISPADHI: CLEARED
PGMTIM: PRESET TO VALUE FOR 10 MHz CKI
WATCHDOG (if enabled):
The device comes out of reset with both the WATCH-
DOG logic and the Clock Monitor detector armed, with
the WATCHDOG service window bits set and the
Clock Monitor bit set. The WATCHDOG and Clock
Monitor
circuits
are
inhibited
WATCHDOG service window bits being initialized high
default to the maximum WATCHDOG service window
of 64k T0 clock cycles. The Clock Monitor bit being
initialized high will cause a Clock Monitor error follow-
ing reset if the clock has not reached the minimum
specified frequency at the termination of reset. A Clock
Monitor error will cause an active low error output on
pin G1. This error output will continue until 16–32 T0
clock cycles following the clock frequency reaching the
minimum specified value, at which time the G1 output
will go high.
during
reset. The
10.7.1 External Reset
The RESET input when pulled low initializes the device. The
RESET pin must be held low for a minimum of one instruc-
tion cycle to guarantee a valid reset. During Power-Up ini-
tialization, the user must ensure that the RESET pin of a
device without the Brownout Reset feature is held low until
the device is within the specified V
CC
voltage. Any rising
edge on the RESET pin while V
operating range may cause unpredictable results. An R/C
circuit on the RESET pin with a delay 5 times (5x) greater
than the power supply rise time is recommended. Reset
should also be wide enough to ensure crystal start-up upon
Power-Up.
RESET may also be used to cause an exit from the HALT
mode.
A recommended reset circuit for this device is shown in
Figure 9
.
10.7.2 On-Chip Brownout Reset
When enabled, the device generates an internal reset as
V
CC
rises. While V
CC
is less than the specified brownout
voltage (V
bor
), the device is held in the reset condition and
the Idle Timer is preset with 00Fx (240–256 t
C
). When V
CC
reaches a value greater than V
bor
, the Idle Timer starts
counting down. Upon underflow of the Idle Timer, the internal
reset is released and the device will start executing instruc-
tions. This internal reset will perform the same functions as
external reset. Once V
is above the V
and this initial Idle
Timer time-out takes place, instruction execution begins and
the Idle Timer can be used normally. If, however, V
drops
below the selected V
, an internal reset is generated, and
the Idle Timer is preset with 00Fx. The device now waits until
V
is greater than V
and the countdown starts over.
When enabled, the functional operation of the device, at
frequency, is guaranteed down to the V
bor
level.
One exception to the above is that the brownout circuit will
insert a delay of approximately 3 ms on power up or any time
the V
drops below a voltage of about 1.8V. The device will
be held in Reset for the duration of this delay before the Idle
Timer starts counting the 240 to 256 t
. This delay starts as
soon as the V
rises above the trigger voltage (approxi-
mately 1.8V). This behavior is shown in
Figure 10
.
10138912
FIGURE 9. Reset Circuit Using External Reset
C
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