Z86C34 datasheet(68/70 Pages) ZILOG

68 / 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

PRECAUTIONS (Continued)

PRECAUTIONS

1. Enabling the transmit interrupt (bit 0 in the ASCI

STAT register) does not make the device ready for

transmitter-related interrupts. The receiver interrupt

(bit 3 in the ASCI STAT register) must also be enabled.

Workaround: For transmit interrupts to be generated,

the RIE bit must also be set. When IRQ3 is generated,

the software should check the STAT register for

details on the interrupt source.

2. When using the device in full-duplex mode under in-

terrupts (both transmit and receive interrupts enabled),

a small window exists where a transmit or receive in-

terrupt may be lost. This situation occurs when an in-

terrupt is generated by one side (either the transmitter

or receiver) and, before the interrupt is serviced, an-

other interrupt is generated by the other side. The sec-

ond interrupt may be lost.

Workaround: The only workaround is not to use

transmitter interrupts when using the ASCI in full-

duplex mode. Use the transmitter in polled mode and

the receiver in interrupt mode for full duplex

operation. In half-duplex operation, this anomaly does

not create a problem.

Z86C34 Datasheet(PDF) 68 Page - Zilog, Inc.