UM001601-0803 1-1
USER’S MANUAL
CHAPTER 1
Z8 MCU PRODUCT OVERVIEW
1.1 Z8 MCU FAMILY OVERVIEW
The ZiLOG Z8 microcontroller (MCU) product line continues to
expand with new product introductions. ZiLOG MCU products
are targeted for cost-sensitive, high-volume applications includ
-
ing consumer, automotive, security, and HVAC. It includes
ROM-based products geared for high-volume production (where
software is stable) and one-time programmable (OTP) equiva
-
lents for prototyping as well as volume production where time to
market or code flexibility is critical (Table 1-1). A variety of
packaging options are available including plastic DIP, SOIC,
PLCC, and QFP.
A generalized Z8 MCU
®
block diagram is shown in Figure 1-1.
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/temper
-
ature ranges available. This allows code written for one MCU
device to be easily ported to another family member.
1.1.1 Key Product Line Features
• General-Purpose Register (GPR) 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 auto latches to hold unused inputs at a known
voltage state.
• Analog Inputs: Three input pins are software programmable
as digital or analog inputs. When in the 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 provides a unique maskable interrupt input.
• Timer/Counter(T/C): The 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 interrupt. 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 output waveform
generation.
• Interrupts: There are six vectored interrupt sources with
software-programmable enable and priority for each of the six
sources.
• Watch-Dog Timer (WDT): An internal WDT circuit is
included as a fail-safe mechanism so that if software strays
outside the bounds of normal operation, the WDT will timeout
and reset the MCU. To maximize circuit robustness and
reliability, the default WDT clock source is an internal RC
circuit (isolated from the device clock source).
• Auto Reset/Low-Voltage Protection: All family devices
have internal Power-On Reset. ROM devices add low-voltage
protection. Low-voltage protection ensures the MCU is in a
known state at all times (in active RUN mode or RESET)
without external hardware (or a device reset pin).
• Low-EMI Operation: Mode is programmable via software or
as a mask option. This new option provides for reduced
radiated emission via clock and output drive circuit changes.
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