ZLP12840 datasheet(27/58 Pages) ZILOG

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PS024406-0106

P R E L I M I N A R Y

Port 3

ZLP12840 OTP MCU

Product Specification

ter; such reads always return a value of 1. Also, when in ANALOG mode, P31 cannot be

used as a stop-mode recovery source because in STOP mode, the comparator is disabled,

and its output will not toggle. The programming of Bit 2 of the P3M register takes prece-

dence over the programming of Bit 1 in determining the function of P31. If both bits are

set, P31 functions as an IR learning amplifier instead of an analog comparator. As shown

in Figure 6, the output of the function selected for P31 can be used as a source for IRQ2

interrupt assertion. The IRQ2 interrupt can be configured to be based upon detecting a ris-

ing, falling, or edge-triggered input change using Bits 6 and 7 of the IRQ register. The P31

output stage signal also goes to the Counter/Timer edge detection circuitry in the same

way that P20 does.

P32 can be used as an interrupt, analog comparator, UART receiver, normal digital input

and as a stop-mode recovery source. When bit 6 of UCTL is set, P32 functions as a receive

input for the UART. When bit 1 of the P3M Register is set, thereby placing the part into

ANALOG mode, P32 functions as an analog comparator, Comp2. The reference voltage

for Comp2 is P33 (PREF2). P32 can be used as a rising, falling or edge-triggered interrupt,

IRQ0, using IRQ register bits 6 and 7. If UART receiver interrupts are not enabled, the

UART receive interrupt is used as the source of interrupts for IRQ0 instead of P32. When

in ANALOG mode P32 cannot be used as a stop-mode recovery source because the com-

parators are turned OFF in STOP mode.

When in ANALOG mode, P33 cannot be read through bit 3 of the Port 3 Register as a dig-

ital input by the CPU. In this case, a read of bit 3 of the Port 3 Register indicates whether a

Stop-mode recovery condition exists. Reading a value of 0 indicates that a Stop-mode

recovery condition does exist; if the ZLP12840 MCU is presently in STOP mode, it will

exit STOP mode. Reading a value of 1 indicates that no condition exists to remove the

ZLP12840 from STOP mode. Additionally, when in ANALOG mode, P33 cannot be used

as an interrupt source. Instead, the existence of a Stop-mode recovery condition can gener-

ate an interrupt, if enabled. P33 can be used as a falling-edge interrupt, IRQ1, when not in

ANALOG mode. IRQ1 is also used as the UART TX interrupt and the UART BRG inter-

rupt. Only one source is active at a time. If bits 7 and 5 of UCTL are set to 1, IRQ1 will

transmit an interrupt when the Transmit Shift Register is empty. If bits 0 and 5 of UCTL

are set to 1 and bit 6 of UCTL is cleared to 0, the BRG interrupts will activate IRQ1.

Comparators and the IR amplifier are powered down by entering STOP mode. For

P30:P33 to be used as a stop-mode recovery source during STOP mode, these inputs must

be placed into digital mode. When in analog mode, do not configure any Port 3 input as a

stop-mode recovery source. The configuration of these inputs must be re-initialized after

stop-mode recovery or power-on reset.

Note:

ZLP12840 Datasheet(PDF) 27 Page - Zilog, Inc.

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