Kawasaki 80C152 - Manual (Page 78)

KS152JB Universal Communications Controller
Technical Specifications
Kawasaki LSI USA, Inc. Page 78 of 120 Ver. 0.9 KS152JB2
There are four modes in which the DMA channel can operate. These are selected by the bits DM
and TM (Demand Mode and Transfer Mode) in DCONn:
The operating modes are described below.
4.1.1 ALTERNATE CYCLE MODE
In Alternate Cycles Mode the DMA is initiated by setting the GO bit in DCONn. Following the
instruction that set the GO bit, one more instruction is executed, and then the first data byte is
transferred from the source address to the destination address. Then another instruction is exe-
cuted, and then another byte of data is transferred, and so on in this manner.
Each time a data byte is transferred, BCRn (Byte Count Register for DMA Channel n) is decre-
mented. When it reaches 0000H, on-chip hardware clears the GO bit and sets the DONE bit, and
the DMA ceases. The DONE bit flags an interrupt.
4.1.2 BURST MODE
Burst Mode differs from Alternate Cycles mode only in that once the data transfer has begun, pro-
gram execution is entirely suspended until BCRn reaches 0000H, indicating that all data bytes
that were to be transferred have been transferred. The interrupt control hardware remains active
DAS IDA Destination Auto-Increment
0
0
1
1 0
1
0
1 External RAM
External RAM
SFR
Internal RAM
no
yes
no
yes
SAS ISA Source Auto-Increment
0
0
1
1 0
1
0
1 External RAM
External RAM
SFR
Internal RAM
no
yes
no
yes
DM TM Operating Mode
0
0
1
1 0
1
0
1 Alternate Cycles Mode
Burst Mode
Serial Port Demand Mode
External Demand Mode