Typewriter User Manual
6- 38 MC68340 USER’S MANUAL MOTOROLA
• If using internal request, select the amount of bus bandwidth to be used by the DMA
(BB field).
• Clear the S/D bit for dual-address transfer.
Channel Status Register (CSR)
• Clear the CSR by writing $7C into it. The DMA cannot be started until the DONE,
BES, BED, CONF, and BRKP bits are cleared.
Function Code Register (FCR)
• Encode the source and destination function codes.
Address Registers (SAR and DAR)
• Write the source and destination addresses.
Byte Transfer Counter (BTC)
• Encode the number of bytes to be transferred.
Channel Control Register (CCR)
• Write a one to the start bit (STR) to allow the transfer to begin.
6.9.2 DMA Channel Example Configuration Code
The following are examples of configuration sequences for a DMA channel in single- and
dual-addressing modes.
***************************************************************************
* MC68340 basic DMA channel register initialization example code.
* This code is used to initialize the 68340's internal DMA channel
* registers, providing basic functions for operation.
* The code sets up channel 1 for external burst request generation,
* single-address mode, long word size transfers.
* Control signals are asserted on the DMA read cycle.
***************************************************************************
Example 1: External Burst Request Generation, Single-Address Transfers.
***************************************************************************
* SIM40 equates
***************************************************************************
MBAR EQU $0003FF00 Address of SIM40 Module Base Address Reg.
MODBASE EQU $FFFFF000 SIM40 MBAR address value
***************************************************************************
* DMA Channel 1 equates
DMACH1 EQU $780 Offset from MBAR for channel 1 regs
DMAMCR1 EQU $0 MCR for channel 1
* Channel 1 register offsets from channel 1 base address
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cale Semiconductor,
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