UPD78F1502AGK-GAK-AX Datasheet, PDF (736/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 18 DMA CONTROLLER
(3) DMA byte count register n (DBCn)
This is a 10-bit register that is used to set the number of times DMA channel n executes transfer. Be sure to set
the number of times of transfer to this DBCn register before executing DMA transfer (up to 1024 times).
Each time DMA transfer has been executed, this register is automatically decremented. By reading this DBCn
register during DMA transfer, the remaining number of times of transfer can be learned.
DBCn can be read or written in 8-bit or 16-bit units. However, it cannot be written during DMA transfer.
Reset signal generation clears this register to 0000H.
Figure 18-3. Format of DMA Byte Count Register n (DBCn)
Address: FFFB6H, FFFB7H (DBC0), FFFB8H, FFFB9H (DBC1)
DBC0H: FFFB7H
DBC1H: FFFB9H
After reset: 0000H R/W
DBC0L: FFFB6H
DBC1L: FFFB8H
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
DBCn 0 0 0 0 0 0
(n = 0, 1)
DBCn[9:0] Number of Times of Transfer
(When DBCn is Written)
Remaining Number of Times of Transfer
(When DBCn is Read)
000H
001H
1024
1
Completion of transfer or waiting for 1024 times of DMA transfer
Waiting for remaining one time of DMA transfer
002H
2
003H
3
Waiting for remaining two times of DMA transfer
Waiting for remaining three times of DMA transfer
•
•
•
3FEH
3FFH
•
•
•
1022
1023
•
•
•
Waiting for remaining 1022 times of DMA transfer
Waiting for remaining 1023 times of DMA transfer
Cautions 1. Be sure to clear bits 15 to 10 to “0”.
2. If the general-purpose register is specified or the internal RAM space is exceeded as a
result of continuous transfer, the general-purpose register or SFR space are written or read,
resulting in loss of data in these spaces. Be sure to set the number of times of transfer that
is within the internal RAM space.
Remark n: DMA channel number (n = 0, 1)
R01UH0004EJ0501 Rev.5.01
720
Jun 20, 2011