Samsung MSYS 5150, Service Manual, Page: 51 / 210

Circuit Description
Samsung Electronics 5-3
Fig.5-3. Uart Data Format
Fig.5-4. External DMA Timing Diagram
EXTERNAL D M A
It brings data from an external device (SCAN_IP:U31)
through EXTDMA channel 1. When the DMA
REQUEST is sent from an external device to
KS32C6100, DMA ACKNOWLEDGE signal is
activated and DMA channel 1 is driven to produce
CHIP SELECT and READ STROBE (/RD) and data is
brought from the external device. It generates the
address, CHIP SELECT and WRITE STROBE (/WR)
in order to move this data to destination memory, and
then stores the data.
In other words, when the external DMA is requested
by an external device, KS32C6100 drives internal
D M A controller, DMA channel 1 is assigned to
external channel, the data is sent from memory to
memory or from external device to memory.
Following timing shows that when DMA REQUEST
(/XDREQ) is generated, DMA A C K N O W L E D G E
(/XDACK) is sent after 2 cycles and the 2 Word Data
is read from external device, and is written into
memory. After that if the DMA REQUEST is
maintained continuously, DMA A C K N O W L E D G E
signal is generated after 4 cycles and the same
operation is repeated.
Following diagram shows one DMA cycle. The
external device (SCAN_IP) using the DMA maintains
continuously DMA request to be activated until
second DMA is performed, so one request brings 2
W ord.