Define bus arbitration. Sketch and describe the internal block diagram of 8254 PIT. Why 8254 is called programmable?
Answers
Explanation:
Microprocessor | 8254 programmable interval timer
Microprocessor | 8254 programmable interval timer8254 is a device designed to solve the timing control problems in a microprocessor. It has 3 independent counters, each capable of handling clock inputs up to 10 MHz and size of each counter is 16 bit. It operates in +5V regulated power supply and has 24 pin signals. All modes are software programmable. The 8254 is an advanced version of 8253 which did not offered the feature of read back command.
Microprocessor | 8254 programmable interval timer8254 is a device designed to solve the timing control problems in a microprocessor. It has 3 independent counters, each capable of handling clock inputs up to 10 MHz and size of each counter is 16 bit. It operates in +5V regulated power supply and has 24 pin signals. All modes are software programmable. The 8254 is an advanced version of 8253 which did not offered the feature of read back command.The basic block diagram of 8254 is:
Answer:
The 8255A is a general purpose programmable I/O device designed to transfer the data from I/O to interrupt I/O under certain conditions as required. It can be used with almost any microprocessor.
It consists of three 8-bit bidirectional I/O ports (24I/O lines) which can be configured as per the requirement.
Ports of 8255A
8255A has three ports, i.e., PORT A, PORT B, and PORT C.
Port A contains one 8-bit output latch/buffer and one 8-bit input buffer.
Port B is similar to PORT A.
Port C can be split into two parts, i.e. PORT C lower (PC0-PC3) and PORT C upper (PC7-PC4) by the control word.
These three ports are further divided into two groups, i.e. Group A includes PORT A and upper PORT C. Group B includes PORT B and lower PORT C. These two groups can be programmed in three different modes, i.e. the first mode is named as mode 0, the second mode is named as Mode 1 and the third mode is named as Mode 2