Using The Timer To Initiate Dma Transfers; Limitations Due To Pin Signal Multiplexing - Intel 386 User Manual

Intel386™ EX EMBEDDED MICROPROCESSOR USER'S MANUAL
configured DMA channel. SIO and SSIO inputs to the DMA are selected by the DMA configu-
ration register (Figure 5-3).
5.2.1.3

Using The Timer To Initiate DMA Transfers

A timer output (OUT1, OUT2) can initiate periodic data transfers by the DMA. A DMA channel
is programmed for the transfer, then a timer output pulse triggers the transfer. The most useful
DMA and timer combinations for this type of transfer are the periodic timer modes (mode 2 and
mode 3) with the DMA block-transfer mode programmed. See Chapter 10, "TIMER/COUNTER
UNIT," and Chapter 12, "DMA CONTROLLER," for more information on how to program the
peripherals.
5.2.1.4

Limitations Due To Pin Signal Multiplexing

Pin signal multiplexing can preclude the simultaneous use of a DMA channel and another periph-
eral or specific peripheral signal (see Figure 5-2). For example, using DMA channel 1 with an
external requester device precludes using SIO channel 1 due to the multiplexed signal pairs
DRQ1/RXD1 and DACK1#/TXD1. Please refer to the Intel386™ EX Microprocessor Pin Mul-
tiplexing Map (Order Number 272587) for a complete diagram of multiplexed signals.
5-4