EM78P258N
8-Bit Microprocessor with OTP ROM
6.9 Timer / Counter
6.9.1 Overview
TimerA (TCCA ) is an 8-bit clock counters. TimerB (TCCB) is a 16-bit clock counter.
TimerC (TCCC) is an 8-bit clock counters that can be extended to 16-bit clock counter
with programmable scalers. TCCA, TCCB, and TCCC can be read and written; and are
cleared at every reset condition.
6.9.2 Function Description
Set predict value
Set predict value
Set predict value
TCCCEN
Set TCCCIF
TCCAEN
TCCBEN
Set TCCBIF
Set TCCAIF
TCCC
TCCB
TCCA
Overflow
TCCCS1 ~ TCCCS0
Overflow
Overflow
System clock
System clock or
External input
8-to-1 MUX
8 Bit
counter
System clock
Fig. 6.12 TIMER Block Diagram
Each signal and block of the above TIMER block diagram is described as follows:
TCCX: Timer A~C register. TCCX increases until it matches with zero, and then
reload the predicted value. When writing a value to TCCX, the predicted value
and TCCX value become the set value. When reading from TCCX, the value
will be the TCCX direct value. When TCCXEN is enabled, the reload of the
predicted value to TCCX, TCCXIE is also enabled. TCCXIF will be set at the
same time. It is an up counter.
Under TCCA Counter (IOC51):
IOC51 (TCCA) is an 8-bit clock counter. It can be read, written, and cleared on
any reset condition and is an UP Counter.
NOTE
■ TCCA timeout period [1/Fosc x (256-TCCA cnt) x 1(CLK=2)]
■ TCCA timeout period [1/Fosc x (256-TCCA cnt) x 2(CLK=4)]
Under TCCB Counter (IOC61):
An 8-bit clock counter is for the least significant byte of TCCBX (TCCB). It can
be read, written, and cleared on any reset condition and is an UP Counter.
Product Specification (V1.0) 06.16.2005
• 53
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
