R01UH0092EJ0110 Rev.1.10
Page 246 of 807
Jul 31, 2012
M16C/64C Group
16. DMAC
16.3.4
DMAC Transfer Cycles
The formula for calculating the number of DMAC transfer cycles is shown below.
Number of transfer cycles per transfer unit = Number of read cycles × j + Number of write cycles × k
Table 16.8
DMAC Transfer Cycles
Transfer Unit
Bus Width
Access
Address
Single-Chip Mode
Memory Expansion Mode
Microprocessor Mode
Number of
read cycles
Number of
write cycles
Number of
read cycles
Number of
write cycles
8-bit transfers
(DMBIT = 1)
16-bit
(BYTE = low)
Even
1
1
1
1
Odd
1
1
1
1
8-bit
(BYTE = high)
Even
N/A
N/A
1
1
Odd
N/A
N/A
1
1
16-bit transfers
(DMBIT = 0)
16-bit
(BYTE = low)
Even
1
1
1
1
Odd
2
2
2
2
8-bit
(BYTE = high)
Even
N/A
N/A
2
2
Odd
N/A
N/A
2
2
DMBIT: Bit in the DMiCON register (i = 0 to 3)
Table 16.9
Coefficients j and k (1/2)
Internal Area
External Area
Internal ROM, RAM
SFR
Multiplex bus
No waits
inserted
Wait
inserted
one wait
inserted
Wait inserted
(1)
one wait
two wait
three wait
j
1
2
2
3
3
4
k
1
2
2
3
3
4
Note:
1.
Depends on the set value of the CSE register.
Table 16.10
Coefficients j and k (2/2)
External Area
Separate bus
No waits
inserted
Wait states
(1)
one wait inserted
(1
φ
+ 1
φ
)
two wait inserted
(1
φ
+ 2
φ
)
three wait inserted
(1
φ
+ 3
φ
)
j
1
2
3
4
k
2
2
3
4
Note:
1.
Depends on the set values of the CSE register.
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