![](http://datasheet.mmic.net.cn/90000/M37641M8-XXXHP_datasheet_3496247/M37641M8-XXXHP_211.png)
Rev.2.00
Aug 28, 2006
page 80 of 148
7641 Group
REJ09B0336-0200
APPLICATION
2.5 DMAC
2.5.2 Related registers
(1) DMAC index and status register
DMAC channel x (x = 0, 1) count register underflow flag (DxUF)
When the corresponding transfer count register Low (address 4616) underflows, this DxUF flag is
set to “1”. Writing “0” into this flag clears it.
DMAC channel x (x = 0, 1) suspend flag (DxSFI)
When an interrupt routine is processed during any DMA operation, the transfer operation is suspended
and the DMAC automatically sets the corresponding DxSFI flag to “1”. As soon as the CPU
completes the interrupt operation, the DMAC clears the DxSFI flag to “0” and resumes the original
operation from the point where it was suspended.
DMAC transfer suspend control bit (DTSC)
This bit specifies the transfer mode which can be suspended by an interrupt process.
DMAC register reload disable bit (DRLDD)
If the DRLDD bit is “1”, when the DMAC channel x transfer count register underflows, the DMAC
channel x source registers and destination registers are disabled from being reloaded from their
latches.
Channel index bit (DCI)
The related registers of channels 1 and 2 are assigned on the same SFR addresses. This DCI bit
specifies the accessible channel.
Fig. 2.5.2 Structure of DMAC index and status register
DMAC index and status register
b7 b6 b5 b4 b3 b2 b1 b0
DMAC index and status register
(DMAIS : address 3F16)
b
0
1
2
4
Name
0
Functions
At reset R W
0
DMAC channel 0 suspend
flag (D0SFI) (Note 1)
DMAC transfer suspend
control bit (DTSC) (Note 2)
DMAC channel 1 count
register underflow flag (D1UF)
0 : No underflow
1 : Underflow generated
0 : Not suspended
1 : Suspended
DMAC channel 1 suspend
flag (D1SFI) (Note 1)
0 : No underflow
1 : Underflow generated
5
0
DMAC register reload
disable bit (DRLDD)
(Note 3)
7
0
Channel index bit (DCI)
0 : Channel 0 accessible
1 : Channel 1 accessible
Accessed registers: Mode register,
source register, destination register,
transfer count register.
0
DMAC channel 0 count
register underflow flag (D0UF)
Fix this bit to “0”.
3
0 : Not suspended
1 : Suspended
0 :Suspending only burst transfers during
interrupt process
1 : Suspending both burst and cycle steal
transfers during interrupt process
0 :Enabling reload of source and
destination registers of both channels
1 : Disabling reload of source and
destination registers of both channels
6
Notes 1: Suspended by an interrupt.
2: Transfer suspended during interrupt process
3: This settings affect the source and destination registers of both channels.
: “0” can be set by software, but “1” cannot be set.