ZiLOG Z8 User Manual

UM001601-0803 6-1
USER’S MANUAL
CHAPTER 6
COUNTER/TIMERS
6.1 INTRODUCTION
The Z8 MCU
®
provides up to two 8-bit counter/timers, T0 and
T1, each driven by its own 6-bit prescaler, PRE0 and PRE1 (Fig
-
ure 6-1). Both counter/timers are independent of the processor
instruction sequence, that relieves software from time-critical
operations such as interval timing or event counting. Some
MCUs offer clock scaling using the SMR register. See the device
product specification for clock available options. The following
description is typical.
Each counter/timer operates in either Single-Pass or Continuous
mode. At the end-of-count, counting either stops or the initial
value is reloaded and counting continues. Under software con
-
trol, new values are loaded immediately or when the end-of-
count is reached. Software also controls the counting mode, how
a counter/timer is started or stopped, and its use of I/O lines. Both
the counter and prescaler registers can be altered while the
counter/timer is running.
Figure 6-1. Counter/Timer Block Diagram
÷2
OSC
D1 (SMR)
÷16
D0 (SMR)
Clock
÷4
Logic
Internal
Clock
External Clock
Internal Clock
Gated Clock
Triggered Clock
T
IN
P31
÷4
6-Bit
Down
Counter
8-Bit
Down
Counter
PRE1
Initial Value
Register
T1
Initial Value
Register
T1
Current Value
Register
Write
Read
Write
Write
Read
Write
6-Bit
Down
Counter
8-Bit
Down
Counter
PRE0
Initial Value
Register
T0
Initial Value
Register
T0
Current Value
Register
÷2
Internal Data Bus
Internal Data Bus
T
OUT
IRQ
4
P36
IRQ
5

ZiLOG Z8 Specifications

General

Brand	ZiLOG
Model	Z8
Category	Desktop
Language	English