Z86E3016PSG Datasheet, PDF (109/348 Pages) Zilog, Inc. – Z86E3016PSG

Z8 CPU
User Manual
91
To avoid losing data, the software must not overwrite the port until the
corresponding interrupt request indicates that the external device has
latched the data.
The software can always read Port 3 output and input handshake lines, but
cannot write to the output handshake line.
The following is the recommended setup sequence when configuring a
Port for handshake operation for the first time after a reset:
• Load P01M or P2M to configure the port for input/output
• Load P3 to set the Output Handshake bit to a logic 1
• Load P3M to select HANDSHAKE mode for the port
Once a data transfer begins, the configuration of the handshake lines
should not be changed until the handshake is completed.
Figures 50 and 51 show detailed operation for the handshake sequence.
UM001602-0904
I/O Ports