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13
Z86C61/62/96
Z8
M
ICROCONTROLLER
and P35 are used as the handshake control /DAV0 and
RDY0 (Data Available and Ready). Handshake signal
assignment is dictated by the I/O direction of the upper
nibble P07-P04. The lower nibble must have the same
direction as the upper nibble to be under handshake
control.
For external memory references, Port 0 can provide ad-
dress bits A11-A8 (lower nibble) or A15-A8 (lower and
upper nibble) depending on the required address space.
If the address range requires 12 bits or less, the upper
nibble of Port 0 can be programmed independently as I/O
while the lower nibble is used for addressing. If one or both
nibbles are needed for I/O operation, they must be config-
ured by writing to the Port 0 Mode register.
In ROMless mode, after a hardware reset, Port 0 lines are
defined as address lines A15-A8, and extended timing is
set to accommodate slow memory access. The initializa-
tion routine includes reconfiguration to eliminate this ex-
tended timing mode (Figure 10).
/P0DS
Port 0 Data Strobe(output, active Low). Signal used
to emulate Port 0 when in ROMless mode.
/P1DS
Port 1 Data Strobe output, active Low). Signal used
to emulate Port 1 when in ROMless mode.
/DTIMERS
Disable Timers (input, active Low). All timers
are stopped by the Low level at this pin. This pin has an
internal pull up resistor.
SCLK
(output). System clock pin.
/SYNC
Instruction SYNC Signal output, active Low). This
signal indicates the last clock of the current executing
instruction.
Port 0
(P07-P00). Port 0 is an 8-bit, nibble programmable,
bidirectional, TTL compatible port. These eight I/O lines
can be configured under software control as a nibble I/O
port, or as an address port for interfacing external memory.
When used as an I/O port, Port 0 may be placed under
handshake control. In this configuration, Port 3, lines P32
OEN
Out
In
PAD
Port 0 (I/O)
Handshake Controls
/DAV0 and RDY0
(P32 and P35)
MCU
4
TTL Level Shifter
Auto Latch
R
≈
500 K
4
Figure 10. Port 0 Configuration