Microprocessor DMA Controller – Learn Microprocessor in simple and easy steps starting from basic to advanced concepts with examples including. Five host microprocessors with peer-to-peer communications were used in the The board contained an Atmel ATS microprocessor, a Precision Motion. The Intel and are Programmable Interval Timers (PITs), which perform timing and To initialize the counters, the microprocessor must write a control word (CW) in this register. This can be done by setting proper values for the pins .

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In the master mode, micrprocessor is used to load the data to the peripheral devices during DMA memory read cycle. Retrieved from ” https: Motorola-Freescale-NXP processors and microcontrollers. By using this site, you agree to the Terms of Use and Privacy Policy.

Once programmed, the channels operate independently. Bits 5 through 0 are the same as the last bits written to the control register. These are bidirectional, data lines which are used to interface the system bus with the internal data bus of DMA controller. OUT will go low on the Clock pulse following a trigger to begin the one-shot pulse, and will remain low until the Counter reaches zero.

If a new count is written to the Counter during a microporcessor pulse, the current one-shot is not affected unless the counter is retriggered.

Microprocessor DMA Controller

These are the four least significant address lines. As stated above, Channel 0 is implemented as a counter. In the master mode, it is used to read data from the peripheral devices during a memory write cycle.


The D3, D2, and D1 bits of the control word set the operating mode of the timer. Views Read Edit View history.

Microprocessor – 8257 DMA Controller

If Gate goes low, counting is suspended, micro;rocessor resumes when it goes high again. Microprocewsor mode is similar to mode 2. Then the microprocessor tri-states all the data bus, address bus, and control bus. Retrieved 21 August It is the active-low three state signal which is used to write the data to the addressed memory location during DMA write operation. The fastest possible interrupt frequency is a little over a half of a megahertz.

NXP Semiconductors Lists of microprocessors.

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In this mode, the microprocezsor acts as a divide-by-n counter, which is commonly used to generate a real-time clock interrupt.

November Learn how and when to remove this template message. OUT will be initially high. The following is a partial list of NXP and Freescale Semiconductor products, including products formerly manufactured by Motorola until The slowest possible frequency, which is also the one normally used by computers running MS-DOS or compatible operating systems, is about The three counters are bit down counters independent of each other, ,icroprocessor can be easily read by the CPU.

The control word register contains 8 bits, labeled D The timer has three counters, numbered 0 to 2. In the slave mode, they act as an input, which selects one of the registers to be read or written. However, the duration of the high and low clock pulses of the output will be different from mode 2.

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However, in free-running counter applications such as in the x86 PC, it is necessary to first write a latch command for the desired channel to the control register, so that both bytes read will belong to one and the same value.

This prevents any serious alternative uses of the timer’s second counter on many x86 systems.

Retrieved from ” https: This signal is used to convert the higher byte of the memory address generated by the DMA controller into the latches. Reprogramming typically happens during video mode changes, when the video BIOS may be executed, and during system management mode and power saving state changes, when the system BIOS may be executed. Unsourced material may be challenged and removed. There are 6 modes in total; for modes 2 and 3, the D3 bit is ignored, so the missing modes 6 and 7 are aliases for modes 2 and 3.

In the Slave mode, it carries command words to and status word from It is an active-low chip select line. This signal is used to receive the hold request signal from the output device.