The data transfer count register is a 16-bit register that counts the number of bytes or words of
data remaining to be transferred. The initial count can be set from 1 to 65,536. A register value
of 0 designates an initial count of 65,536.
The data transfer count register is decremented automatically after each byte or word is transferred.
When its value reaches 0, indicating that the designated number of bytes or words have been
transferred, a CPU interrupt is generated with the vector of the interrupt that requested the data transfer.
6.2.5 Data Transfer Enable Registers A to F (DTEA to DTEF)
These six registers designate whether an interrupt starts the DTC. The bits in these registers are
assigned to interrupts as indicated in table 6-3. No bits are assigned to the NMI, FOVI, OVI, and
ERI interrupts, which cannot request data transfers.
Table 6-3 Assignment of Data Transfer Enable Registers
Interrupt
Source or
Register Module
Bits 7 to 4
7
DTEA
IRQ
0
—
Note:
Bits marked “—” should always be cleared to 0.
If the bit for a certain interrupt is set to 1, that interrupt is regarded as a request for DTC service.
If the bit is cleared to 0, the interrupt is regarded as a CPU interrupt request.
Bit
7
6
5
4
3
2
1
0
Initial value
0
0
0
0
0
0
0
0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Interrupt
Source or
Module
Bits 3 to 0
3
—
6
—
5
—
4
2
—
1
—
0
IRQ
0
IRQ
1
IRQ
1
DTEB
IRQ
2
, IRQ
3
—
—
IRQ
3
IRQ
2
IRQ
4
, IRQ
5
—
—
IRQ
5
IRQ
4
DTEC
16-Bit FRT1
—
OCIB1 OCIA1
ICI1
16-Bit FRT2
—
OCIB2 OCIA2
ICI2
DTED
16-Bit FRT3
—
OCIB3 OCIA3
ICI3
8-Bit Timer
—
—
CMIB CMIA
DTEE
SCI1
—
TXI1
RXI1
—
SCI2
—
TXI2
RXI2
—
DTEF
A/D converter
—
—
—
ADI
—
—
—
—
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