Z86L71 datasheet(36/61 Pages) ZILOG

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Z86L70/71/75/C71

IR/Low-Voltage Microcontroller

Zilog

1-36

P R E L I M I N A R Y

DS97LVO0500

FUNCTIONAL DESCRIPTION (Continued)

Ping-Pong Mode

This operation mode is only valid in Transmit Mode. T8

and T16 need to be programmed in Single-Pass Mode

(CTR0 D6, CTR2 D6) and Ping-Pong Mode needs to be

programmed in CTR1 D3, D2. The user can begin the op-

eration by enabling either T8 or T16 (CTR0 D1 or CTR2

D7). For example, if T8 is enabled, T8_OUT is set to this

initial value (CTR1 D1). According to T8_OUT's level,

TC8H or TC8L is loaded into T8. After the terminal count

is reached, T8 is disabled and T16 is enabled. T16_OUT

switches to its initial value (CTR1 D0), data from TC16H

and TC16L is loaded, and T16 starts to count. After T16

reaches the terminal count it stops, T8 is enabled again,

and the whole cycle repeats. Interrupts can be allowed

when T8 or T16 reaches terminal control (CTR0 D1, CTR2

D1). To stop the Ping-Pong operation, write 00 to bits D3

and D2 of CTR1.

Note:Enabling

Ping-Pong

operation

while

the

counter/timers are running may cause intermittent

counter/timer function. Disable the counter/timers, then

reset the status flags prior to instituting this operation.

To Initiate Ping-Pong Mode

First, make sure both counter/timers are not running. Then

set T8 into Single-Pass Mode (CTR0 D6), set T16 into Sin-

gle-Pass Mode (CTR2 D6), and set Ping-Pong Mode

(CTR1 D2, D3). These instructions do not have to be in

any particular order. Finally, start Ping-Pong Mode by en-

abling either T8 (CTR0 D7) or T16 (CTR2 D7).

During Ping-Pong Mode

The enable bits of T8 and T16 (CTR0 D7, CTR2 D7) will

be alternately set and cleared by hardware. The time-out

bits (CTR0 D5, CTR2 D5) will be set every time the

counter/timers reach the terminal count.

Figure 27. Ping-Pong Mode

Enable

TC8

Time-Out

Enable

TC16

Time-Out

Ping-Pong

CTR1 D3,D2

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