Microprocessors and Microcontrollers: Unit IV: (c) Programmable Interval Timer (PIT/C) 8253/8254
Programmable Interval Timer (PIT/C) 8253/8254
Microprocessors and Microcontrollers
The 8253/54 solves one of the most common problem in any microcomputer system - the generation of accurate time delays under software control.
UNIT IV
Chapter 10
(c) Programmable Interval Timer (PIT/C) 8253/8254
Contents
10.1
Features
10.2
Block Diagram ……. May-13,14,16, ….. Dec.-15, 16 …. Marks 16
10.3
Operational Description …… Dec.-11, 16 ….. Marks 8
10.4
Mode Definition ….. May-07, June-07, …. Dec.-11, 12, 15,17 … Marks 16
10.5
Programming Examples
10.6
Interfacing of 8253/54 in I/O Mapped I/O
10.7
Two Marks Questions with Answers
10.8
University Questions with Answers (Long Answered Questions)
The
8253/54 solves one of the most common problem in any microcomputer system - the
generation of accurate time delays under software control. Instead of setting
up timing loops in system software, the programmer configures the 8253/54 to
match his requirements, initializes one of the counters of the 8253/54 with the
desired quantity, then upon command the 8253/54 will count out the delay and
interrupt the CPU when it has completed its tasks. It is easy to see that the
software overhead is minimum and that multiple delays can be easily be
maintained by assignment of priority levels.
The
8253/54 includes three identical 16 bit counters that can operate
independently. To operate a counter, a 16-bit count is loaded in its register
and, on command, it begins to decrement the count until it reaches 0. At the
end of the count, it generates a pulse that can be used to interrupt the CPU.
The counter can count either in binary or BCD. In addition, a count can be read
by the CPU while the counter is decrementing. In this chapter, we are going to
study two timer ICs 8253 and 8254. The 8254 is a superset of 8253. The
functioning of these two ICs are almost similar along with the pin
configuration. Only the differences are :
1.
Operating frequency 0 - 2.6 MHz. Operating
frequency 0-10 MHz.
2.
Uses N-MOS technology. - Uses H-MOS
technology.
3.
Read-Back command not available. - Read-Back
command available.
4.
Reads and writes of the same counter cannot be interleaved. - Reads and writes of the same counter
can be interleaved.
In this chapter, where the things are common 8253/54 is mentioned and 8254 is mentioned specifically for giving only information about 8254.
Microprocessors and Microcontrollers: Unit IV: (c) Programmable Interval Timer (PIT/C) 8253/8254 : Tag: : Microprocessors and Microcontrollers - Programmable Interval Timer (PIT/C) 8253/8254