Z8
®
CPU
User Manual
UM001604-0108 Z8
®
CPU Product Overview
1
Z8
®
CPU Product Overview
Zilog’s Z8
®
microcontroller (MCU) product line continues to expand with new product
introductions. Zilog MCU products are targeted for cost-sensitive, high-volume applica-
tions including consumer, automotive, security, and HVAC. It includes ROM-based prod-
ucts geared for high-volume production (where software is stable) and one-time
programmable (OTP) equivalents for prototyping as well as volume production where
time to market or code flexibility is critical (see Table 1 on page 3). A variety of packaging
options are available including plastic DIP, SOIC, PLCC, and QFP.
A generalized Z8 CPU block diagram is displayed in Figure 1 on page 2. The same on-
chip peripherals are used across the MCU product line with the primary differences being
the amount of ROM/RAM, number of I/O lines present, and packaging/temperature
ranges available. This allows code written for one MCU device to be easily ported to
another family member.
Key Features
The key features include:
General-Purpose Register File—Every RAM register acts like an accumulator, speeding
instruction execution and maximizing coding efficiency. Working register groups allow
fast context switching.
Flexible I/O—I/O byte, nibble, and/or bit programmable as inputs or outputs. Outputs are
software programmable as open-drain or push–pull on a port basis. Inputs are Schmitt-
Triggered with autolatches to hold unused inputs at a known voltage state.
Analog Inputs—Three input pins are software programmable as digital or analog inputs.
When in analog mode, two comparator inputs are provided with a common reference
input. These inputs are ideal for a variety of common functions, including threshold level
detection, analog-to-digital conversion, and short circuit detection. Each analog input pro-
vides a unique maskable interrupt input.
Timer/Counter—The Timer/Counter (T/C) consists of a programmable 6-bit prescaler and
8-bit downcounter, with maskable interrupt upon end-of-count. Software controls T/C
load/start/stop, countdown read (at any time on the fly), and maskable end-of-count inter-
rupt. Special functions available include T
IN
(external counter input, external gate input,
or external trigger input) and T
OUT
(external access to timer output or the internal system
clock). These special functions allow accurate hardware input pulse measurement and out-
put waveform generation.
Interrupts—There are six vectored interrupt sources with software-programmable enable
and priority for each of the six sources.
Watchdog Timer—An internal Watchdog Timer (WDT) circuit is included as a fail-safe
mechanism so that if software strays outside the bounds of normal operation, the WDT is
used to time-out and reset the MCU. To maximize circuit robustness and reliability, the
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