z8e001 ZiLOG Semiconductor, z8e001 Datasheet - Page 30

• Manufacturer Part Number: z8e001
• Description: Feature-rich Z8plus One-time Programmable Otp Microcontroller
• Manufacturer: ZiLOG Semiconductor

Z8E001
Z8Plus OTP Microcontroller
RESET CONDITIONS
After a hardware RESET, the timers are disabled. See Table
4 for timer control, value, and auto-initialization register
status after RESET.
I/O PORTS
The Z8E001 has 13 lines dedicated to input and output.
These lines are grouped into two ports known as Port A and
Port B. Port A is an 8-bit port, bit programmable as either
inputs or outputs. Port B can be programmed to provide
standard input/output or the following special functions:
timer0 output, comparator input, SMR input, and external
interrupt inputs.
All ports have push-pull CMOS outputs. In addition, the
outputs of Port A on a bit-wise basis can be configured for
open-drain operation.The ports operate on a bit-wise basis.
As such, the register values for/at a given bit position only
affect the bit in question.
Each port is defined by a set of four control registers. See
Figure 27.
Directional Control and Special Function
Registers
Each port on the Z8E001 has a dedicated Directional Con-
trol Register that determines (on a bit-wise basis) whether
a given port bit operates as either an input or an output.
Each port on the Z8E001 has a Special Function Register
that, in conjunction with the Directional Control Register,
implements (on a bit-wise basis), any special functionality
that can be defined for each particular port bit.
READ/WRITE OPERATIONS
The control for each port is done on a bit-wise basis. All
bits are capable of operating as inputs or outputs, depending
upon the setting of the portÕs Directional Control Register.
If configured as an input, each bit is provided a Schmitt-
trigger. The output of the Schmitt-trigger is latched twice
to perform a synchronization function, and the output of the
synchronizer is fed to the port input register, which can be
read by software.
A write to a port input register has the effect of updating
the contents of the input register, but subsequent reads do
not necessarily return the same value that was written. If the
bit in question is defined as an input, the input register for
30
P R E L I M I N A R Y
Input and Output Value Registers
Each port has an Output Value Register and a pF Input Val-
ue Register. For port bits configured as an input by means
of the Directional Control Register, the Input Value Reg-
ister for that bit position contains the current synchronized
input value.
For port bits configured as an output by means of the Di-
rectional Control Register, the value held in the correspond-
ing bit of the Output Value Register is driven directly onto
the output pin. The opposite register bit for a given pin (the
output register bit for an input pin and the input register bit
for an output pin) holds their previous value. These bits are
not changed and donÕt have any effect on the hardware.
that bit position contains the current synchronized input val-
ue. Thus, writes to that bit position is overwritten on the next
clock cycle with the newly sampled input data. However,
if the particular port bit is programmed as an output, the in-
put register for that bit retains the software-updated value.
The port bits that are programmed as outputs do not sample
the value being driven out.
Any bit in either port can be defined as an output by setting
the appropriate bit in the directional control register. If such
is the case, the value held in the appropriate bit of the port
output register is driven directly onto the output pin.
Register
Port B Special Function
Port B Directional Control
Port B Output Value
Port B Input Value
Port A Special Function
Port A Directional Control
Port A Output Value
Port A Input Value
Table 7. Z8E001 I/O Ports Registers
Address
OD7H
0D6H
0D5H
0D4H
0D3H
0D2H
0D1H
0D0H
DS001101-Z8X0400
Identifier
PTBSFR
PTBDIR
PTBOUT
PTBIN
PTASFR
PTADIR
PTAOUT
PTAIN
ZiLOG