COP820 datasheet(15/35 Pages) NSC

15 / 35 page

Reset (Continued)

The user must set the BUSY flag immediately upon entering

the Slave mode. This will ensure that all data bits sent by the

Master will be shifted properly. After eight clock pulses the

BUSY flag will be cleared and the sequence may be re-

peated. (See

Figure 7).

TABLE 5.

Config. Config.

Fun.

Operation

Bit

Int.

MICROWIRE

Master

TRI-STATE

Int.

MICROWIRE

Master

Ext.

MICROWIRE

Slave

TRI-STATE

Ext.

MICROWIRE

Slave

Timer/Counter

The device has a powerful 16-bit timer with an associated

16-bit register enabling it to perform extensive timer func-

tions. The timer T1 and its register R1 are each organized as

two 8-bit read/write registers. Control bits in the register CN-

TRL allow the timer to be started and stopped under soft-

ware control. The timer-register pair can be operated in one

of three possible modes.

Table 6 details various timer oper-

ating modes and their requisite control settings.

MODE 1. TIMER WITH AUTO-LOAD REGISTER

In this mode of operation, the timer T1 counts down at the in-

struction cycle rate. Upon underflow the value in the register

R1 gets automatically reloaded into the timer which contin-

ues to count down. The timer underflow can be programmed

to interrupt the microcontroller. A bit in the control register

CNTRL enables the TIO (G3) pin to toggle upon timer under-

flows. This allows the generation of square-wave outputs or

pulse width modulated outputs under software control

(

Figure 8).

MODE 2. EXTERNAL COUNTER

In this mode, the timer T1 becomes a 16-bit external event

counter. The counter counts down upon an edge on the TIO

pin. Control bits in the register CNTRL program the counter

to decrement either on a positive edge or on a negative

edge. Upon underflow the contents of the register R1 are au-

tomatically copied into the counter. The underflow can also

be programmed to generate an interrupt (

Figure 9).

TABLE 6. Timer Operating Modes

CNTRL

Timer

Bits

Operation Mode

T Interrupt

Counts

765

0 0 0

External Counter w/Auto-Load Reg.

Timer Underflow

TIO Pos. Edge

0 0 1

External Counter w/Auto-Load Reg.

Timer Underflow

TIO Neg. Edge

0 1 0

Not Allowed

0 1 1

Not Allowed

1 0 0

Timer w/Auto-Load Reg.

Timer Underflow

1 0 1

Timer w/Auto-Load Reg./Toggle TIO Out

Timer Underflow

1 1 0

Timer w/Capture Register

TIO Pos. Edge

1 1 1

Timer w/Capture Register

TIO Neg. Edge

DS011208-24

FIGURE 8. Timer/Counter Auto

Reload Mode Block Diagram

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