Intel 8237 - Internal Registers

Internal Registers

The internal registers used in the 8237 for data transfer are as follows:

  • Base address register: To store the initial address from where data transfer will take place
  • Base word count register: To store the number of transfers to be performed
  • Current address register: To store the current address from where data is being transferred
  • Current word count register: To store the number of transfers remaining to be performed
  • Temporary address register: To hold address of data during memory-to-memory transfer
  • Temporary word count register: To hold number of transfers to be performed in memory-to-memory transfer
  • Mode register: 8-bit register which stores the channel to be used, the operating mode, i.e. the transfer mode, and other transfer parameters
  • Command register: 8-bit register which initializes the channel to be used for data transfer
  • Request register: 8-bit register used to indicate which channel is requesting for data transfer
  • Mask register: 8-bit register used to mask a particular channel from requesting for DMA service
  • Status register: 8-bit register used to indicate which channel is currently under DMA service and some other parameters

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