Z8F6421PM020SC Datasheet, PDF (182/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
162
Configuring DMA0 and DMA1 for Data Transfer
Follow these steps to configure and enable DMA0 or DMA1:
1. Write to the DMAx I/O Address register to set the Register File address identifying the
on-chip peripheral control register. The upper nibble of the 12-bit address for on-chip
peripheral control registers is always FH. The full address is {FH, DMAx_IO[7:0]}
2. Determine the 12-bit Start and End Register File addresses. The 12-bit Start Address
is given by {DMAx_H[3:0], DMA_START[7:0]}. The 12-bit End Address is given by
{DMAx_H[7:4], DMA_END[7:0]}.
3. Write the Start and End Register File address high nibbles to the DMAx End/Start
Address High Nibble register.
4. Write the lower byte of the Start Address to the DMAx Start/Current Address register.
5. Write the lower byte of the End Address to the DMAx End Address register.
6. Write to the DMAx Control register to complete the following:
– Select loop or single-pass mode operation
– Select the data transfer direction (either from the Register File RAM to the on-
chip peripheral control register; or from the on-chip peripheral control register to
the Register File RAM)
– Enable the DMAx interrupt request, if desired
– Select Word or Byte mode
– Select the DMAx request trigger
– Enable the DMAx channel
DMA_ADC Operation
DMA_ADC transfers data from the ADC to the Register File. The sequence of operations
in a DMA_ADC data transfer is:
1. ADC completes conversion on the current ADC input channel and signals the DMA
controller that two-bytes of ADC data are ready for transfer.
2. DMA_ADC requests control of the system bus (address and data) from the eZ8 CPU.
3. After the eZ8 CPU acknowledges the bus request, DMA_ADC transfers the two-byte
ADC output value to the Register File and then returns system bus control back to the
eZ8 CPU.
4. If the current ADC Analog Input is the highest numbered input to be converted:
– DMA_ADC resets the ADC Analog Input number to 0 and initiates data
conversion on ADC Analog Input 0.
– If configured to generate an interrupt, DMA_ADC sends an interrupt request to
the Interrupt Controller
PS019915-1005
Direct Memory Access Controller