Freescale Semiconductor, Inc.
DAR1, DAR2
$790, $7B0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
A31
A30
A29
A28
A27
A26
A25
A24
A23
A22
A21
A20
A19
A18
A17
A16
RESET:
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
A15
A14
A13
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
RESET:
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U = Unaffected by reset
Supervisor/User
During the DMA write cycle, this register drives the address on the address bus. This
register can be programmed to increment (CCR DAPI bit set) or remain constant (CCR
DAPI bit cleared) after each operand transfer.
The register is incremented using unsigned arithmetic and will roll over if overflow occurs.
For example, if a register contains $FFFFFFFF and is incremented by 1, it will roll over to
$00000000. This register can be incremented by 1, 2, or 4, depending on the size of the
operand and the starting address. If the operand size is byte, the register is always
incremented by 1. If the operand size is word and the starting address is even-word
aligned, the register is incremented by 2. If the operand size is long word and the address
is even-word aligned, the register is incremented by 4. The DAR value must be aligned to
an even-word boundary if the transfer size is word or long word; otherwise, the CSR
CONF bit is set, and the transfer does not occur.
When read, this register always contains the next destination address. If a bus error
terminates the transfer, this register contains the next destination address that would have
been run had the error not occurred.
6.7.8 Byte Transfer Counter Register (BTC)
The BTC is a 32-bit register that contains the number of bytes left to transfer in a given
block. This register is accessible in either supervisor or user space. The BTC can always
be read or written to when the DMA module is enabled (i.e., the STP bit in the MCR is
cleared).
BTC1, BTC2
$794, $7B4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
A31
A30
A29
A28
A27
A26
A25
A24
A23
A22
A21
A20
A19
A18
A17
A16
RESET:
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
A15
A14
A13
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
RESET:
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U = Unaffected by reset
Supervisor/User
6- 34
MC68340 USER’S MANUAL
MOTOROLA
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