
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.
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 D (DTEA to DTED)
These four 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
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.
Only the 16 interrupts indicated in table 6-3 can request DTC service. DTE bits not assigned to
any interrupt (indicated by “—” in table 6-3) should be left cleared to “0.”
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
Interrupt Source
Module
Register Module
Bits 7 to 4
7
—
Bits 3 to 0
3
—
6
—
5
—
4
2
—
1
—
0
DTEA
IRQ
0
IRQ
0
IRQ
1
IRQ
1
DTEB
16-Bit FRT1
—
OCIB OCIA
ICI
16-Bit FRT2
—
OCIB OCIA
ICI
DTEC
16-Bit FRT3
—
OCIB OCIA
ICI
8-Bit Timer
—
—
CMIB CMIA
DTED
SCI
—
TXI
RXI
—
A/D converter
—
—
—
ADI
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