Z86E3016PSG Datasheet, PDF (108/348 Pages) Zilog, Inc. – Z86E3016PSG

Z8 Family of Microcontrollers
User Manual
90
Table 17. Port 3 Line Functions (Continued)
Function
Interrupt Requests
Serial Input (UART)
Serial Output (UART)
SPI Slave Select
SPI Clock
Counter/Timer
External Memory Status
Line
P30
P31
P32
P33
P30
P37
P35
P34
P31
P36
P34
Signal
IRQ3
IRQ2
IRQ0
IRQ1
DI
DO
SS
SK
T_IN
T_OUT
DM
Port Handshake
When Ports 0, 1, and 2 are configured for handshake operation, a pair of
lines from Port 3 are used for handshake controls. The handshake controls
are interlocked to properly time asynchronous data transfers between the
Z8^® and a peripheral. One control line (DAV) functions as a strobe from
the sender to indicate to the receiver that data is available. The second
control line (RDY) acknowledges receipt of the sender’s data, and indi-
cates when the receiver is ready to accept another data transfer.
In input mode, data is latched into the Port’s input register by the first
DAV signal, and is protected from being overwritten if additional pulses
occur on the DAV line. This overwrite protection is maintained until the
port data is read. In output mode, data written to the port is not protected
and can be overwritten by the Z8^® CPU during the handshake sequence.
I/O Ports
UM001602-0904