COP410C Datasheet, PDF (9/20 Pages) National Semiconductor (TI) – Single-Chip CMOS Microcontrollers

Functional Description (Continued)
HALT MODE
The COP410C 411C is a fully static circuit therefore the
user may stop the system oscillator at any time to halt the
chip The chip also may be halted by the HALT instruction or
by forcing CKO high when it is used as a HALT I O port
Once in the HALT mode the internal circuitry does not re-
ceive any clock signal and is therefore frozen in the exact
state it was in when halted All information is retained until
continuing The HALT mode is the minimum power dissipa-
tion state
The HALT mode has slight differences depending upon the
type of oscillator used
a 1-pin oscillator RC or external
The HALT mode may be entered into by either program
control (HALT instruction) or by forcing CKO to a logic
‘‘1’’ state
The circuit may be awakened by one of two different
methods
1) Continue function By forcing CKO to a logic ‘‘0’’ the
system clock is re-enabled and the circuit continues to
operate from the point where it was stopped
2) Restart Forcing the RESET pin to a logic ‘‘0’’ will re-
start the chip regardless of HALT or CKO (see initiali-
zation)
b 2-pin oscillator crystal
The HALT mode may be entered into by program control
(HALT instruction) which forces CKO to a logic ‘‘1’’ state
The circuit can be awakened only by the RESET function
flip-flop which is an indicator of the HALT status An exter-
nal signal can override this pin to start and stop the chip By
forcing a high level to CKO the chip will stop as soon as
CKI is high and the CKO output will go high to keep the chip
stopped By forcing a low level to CKO the chip will contin-
ue and CKO output will go low
All features associated with the CKO I O pin are available
with the 24-pin package only
OSCILLATOR OPTIONS
There are three options available that define the use of CKI
and CKO
a Crystal-Controlled Oscillator CKI and CKO are connect-
ed to an external crystal The instruction cycle time
equals the crystal frequency divided by 16 (optionally by 8
or 4)
b External Oscillator CKI is configured as LSTTL-compati-
ble input accepting an external clock signal The external
frequency is divided by 16 (optionally by 8 or 4) to give
the instruction cycle time CKO is the HALT I O port
c RC-Controlled Oscillator CKI is configured as a single pin
RC-controlled Schmitt trigger oscillator The instruction
cycle equals the oscillation frequency divided by 4 CKO
is the HALT I O port
The RC oscillator is not recommended in systems that re-
quire accurate timing or low current The RC oscillator
draws more current than an external oscillator (typically an
additional 100 mA at 5V) However when the part halts it
stops with CKI high and the halt current is at the minimum
Halt I O Port
TL DD 5015 – 7
CKO Pin Options
In a crystal-controlled oscillator system CKO is used as an
output to the crystal network CKO will be forced high during
the execution of a HALT instruction thus inhibiting the crys-
tal network If a 1-pin oscillator system is chosen (RC or
external) CKO will be selected as HALT and is an I O
TL DD 5015 – 8
FIGURE 6 COP410C Oscillator
Crystal or Resonator
Crystal
Value
32 kHz
455 kHz
2 096 MHz
4 0 MHz
R1
220k
5k
2k
1k
Component Value
R2 C1 pF C2 pF
20M 30
10M 80
1M
30
1M
30
5-36
40
6-36
6-36
RC-Controlled
Oscillator
R
C
Cycle
Time
15k 82 pF 4-9 ms
30k 82 pF 8-16 ms
47k 100 pF 16-32 ms
Note 15k ^s R ^s 150k
50 pf ^s C ^s 150 pF
V_CC
t_{4 5V}
t_{4 5V}
2 4 to 4 5
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