Z86C34 datasheet(28/70 Pages) ZILOG

28 / 70 page

Z86C34/C35/C36/C44/C45/C46

CMOS Z8® MCUs with ASCI UART

ZiLOG

P R E L I M I N A R Y

DS007601-Z8X0499

PIN FUNCTIONS (Continued)

Auto Latch.

The Auto Latch places valid CMOS levels on

all CMOS inputs (except P33–P31) that are not externally

driven. Whether this level is 0 or 1 cannot be determined.

A valid CMOS level, rather than a floating node, reduces

excessive supply current flow in the input buffer. Auto

Latches are available on Port 0, Port 1, Port 2, and P30.

There are no Auto Latches on P31, P32, and P33.

Note: Deletion of all Port Auto Latches is available as a ROM

Mask option. The Auto Latch Delete option is selected

by the customer when the ROM code is submitted.

RESET (input, active Low).

Initializes the MCU. Reset is

accomplished either through Power-On Reset, Watch-Dog

Timer reset, Stop-Mode Recovery, or external reset. During

Power-On Reset and Watch-Dog Reset, the internally-gen-

erated reset is driving the RESET pin Low for the POR time.

Any devices driving the RESET line must be open-drain to

avoid damage from a possible conflict during RESET con-

ditions. RESET depends on oscillator operation to achieve

full reset conditions, except for conditions wherein a WDT

reset is permanently enabled. Pull-up is provided internally.

Note: The RESET pin is not available on devices in the 28-pin

package.

After the POR time, RESET is a Schmitt-triggered input.

During the RESET cycle, DS is held active Low while AS

cycles at a rate of TPC/2. Program execution begins at lo-

cation 000Ch, after the RESET is released. For Power-On

Reset, the reset output time is TPOR ms.

When program execution begins, AS and DS toggles only

for external memory accesses. The Z8 does not reset

WDTMR

, SMR, P2M, PCON, and P3M registers on a Stop-

Mode Recovery operation or from a WDT reset out of STOP

mode.

Figure 16. Port 3 Conﬁguration

P34 OUT

P31

–

REF (P33)

P34

PAD

P37 OUT

P32

–

REF (P33)

0 P34, P37 Standard Output

1 P34, P37 Comparator Output

PCON

P37

PAD

Z86C34 Datasheet(PDF) 28 Page - Zilog, Inc.

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