Z380 Datasheet, PDF (21/115 Pages) Zilog, Inc. – MICROPROCESSOR

ZILOG
I/O Transactions
I/O transactions move data to or from an external periph-
eral when the Z380 MPU performs an I/O access. All I/O
transactions occur referenced to the IOCLK signal, when
it is a divided-down version of the BUSCLK signal. BUSCLK
may be divided by a factor of from two to eight to form the
MICROPROCESSOR
IOCLK, under program control. An example of this division
is shown, for the four possible divisors, in Figure 7. Note
that the IOCLK divider is synchronized (i.e., starts with a
known timing relationship) at the trailing edge of /RESET.
This is discussed in the Reset Section.
BUSCLK
IOCLK (X2)
IOCLK (X4)
IOCLK (X6)
IOCLK (X8)
Figure 7. IOCLK Timing
PS010001-0301