COP245C datasheet(9/24 Pages) NSC

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Functional Description (Continued)

HALT MODE

The COP244C245C224C225C226C is a FULLY STAT-

IC circuit therefore the user may stop the system oscillator

at any time to halt the chip The chip may also be halted by

the HALT instruction or by forcing CKO high when it is

mask-programmed as a HALT IO port Once in the HALT

mode the internal circuitry does not receive any clock sig-

nal and is therefore frozen in the exact state it was in when

halted All information is retained until continuing The chip

may be awakened by one of two different methods

Continue function by forcing CKO low if it mask-pro-

grammed as a HALT IO port the system clock is re-en-

abled and the circuit continues to operate from the point

where it was stopped

Restart by forcing the RESET pin low (see Initializa-

tion)

The HALT mode is the minimum power dissipation state

CKO PIN OPTIONS

a Two-pin oscillator(Crystal) See

Figure 6a

In a crystal controlled oscillator system CKO is used as

an output to the crystal network The HALT mode may be

entered by program control (HALT instruction) which

forces CKO high thus inhibiting the crystal network The

circuit can be awakened only by forcing the RESET pin to

a logic ‘‘0’’ (restart)

b One-pin oscillator(RC or external) See

Figure 6b

If a one-pin oscillator system is chosen two options are

available for CKO

CKO can be selected as the HALT IO port In that

case it is an IO flip-flop which is an indicator of the

HALT status An external signal can over-ride 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

CKO output will stay high to keep the chip stopped if

the external driver returns to high impedance state

By forcing a low level to CKO the chip will continue

and CKO will stay low

As another option CKO can be a general purpose in-

put read into bit 2 of A (accumulator) upon execution

of an INIL instruction

OSCILLATOR OPTIONS

There are three basic clock oscillator configurations avail-

able as shown by

Figure 5

a Crystal Controlled Oscillator CKI and CKO are connect-

ed to an external crystal The instruction cycle time equals

the crystal frequency optionally divided by 4 8 or 16

b External Oscillator The external frequency is optionally

divided by 4 8 or 16 to give the instruction cycle time

CKO is the HALT IO port or a general purpose input

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 IO port or a general purpose input

Figure 7 shows the clock and timer diagram

COP245C AND COP225C 24-PIN PACKAGE OPTION

If the COP244C224C is bonded in a 24-pin package it be-

comes the COP245C225C illustrated in

Figure 2 Connec-

tion diagrams Note that the COP245C225C does not con-

tain the four general purpose IN inputs (IN3 – IN0) Use of

this option precludes of course use of the IN options inter-

rupt feature external event counter feature

Note

If user selects the 24-pin package options 9 10 19 and 20 must be

selected as a ‘‘2’’ See option list

COP226C 20-PIN PACKAGE OPTION

If the COP225C is bonded as 20-pin device it becomes the

COP226C

Note that the COP226C contains all the

COP225C pins except D0 D1 G0 and G1

Block Diagram

TLDD8422 – 8

FIGURE 6a Halt ModeTwo-Pin Oscillator

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