TMP92CF30
2009-06-12
92CF30-205
3.10.3 An Example of Calculating HDMA Transfer Time
The following shows an example of calculating the HDMA transfer time when SDRAM is used
as the transfer source.
•
Transfer from SDRAM to internal SRAM
Conditions:
System clock (f
SYS
)
: 60 MHz
SDRAM read cycle
: Full page (5-1-1-1), 16-bit data bus
16-bit data bus
SDRAM Auto Refresh interval: 936 states (15.6
μ
s)
Internal RAM write cycle
: 1 state, 32-bit data bus
Number of bytes to transfer : 512 bytes
Calculation example:
Transfer time
=
(SDRAM read time
+
SRAM write time)
×
transfer count
+
(SDRAM burst start
+
stop time)
+
(Precharge time
+
Auto Refresh time)
×
Auto Refresh count
(a)
Read/write time
(SDRAM read 1 state
×
2
+
Internal RAM write 1 state)
×
512 bytes/4 bytes
=
384 states
×
1/60 MHz
=
6.4
μ
s
(b)
Burst start/stop time
Start (TRCD: 2CLK) 5 states
+
Stop 2 states
=
7states/60 MHz
=
0.117
μ
s
(c)
Auto Refresh time
Based on the above (a), Auto Refresh occurs once or zero times in 384 states. It
is assumed that Auto Refresh occurs once here.
(Precharge (TRP: 2CLK) 2 states
+
AREF (TRC: 5CLK) 5 states)
×
AREF once
=
7 states
×
1/60 MHz
=
0.117
μ
s
Total transfer time
=
(a)
+
(b)
+
(c)
=
6.4
μ
s
+
0.117
μ
s
+
0.117
μ
s
=
6.634
μ
s
Summary of Contents for TLCS-900/H1 Series
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