Toshiba H1 Series - Manual (Page 108)

TMP92CZ26A
92CZ26A-105
Sample3) Calculation example for CPU
+ LDMA + ARDMA
Conditions:
CPU operating speed(f
SYS
) : 60 MHz
Display RAM : 16-bit external SDRAM
Display size : QVGA (320seg
× 240com)
Display quality : 65536 colors (TFT)
Refresh rate : 70 Hz (including 20 clocks of dummy cycles)
SDRAM auto refresh : Every 936 states (15.6 μs)
Calculation example:
t
STOP
(LDMA)
=((SegNum × K / 8) × t
LRD
)
+ (8 / f
SYS
[Hz])
= ((320 Ч16 / 8) Ч 1 / f
SYS
[Hz] / 2) + (8 / f
SYS
[Hz])
= ((640) × 16.67 [ns] / 2) + 133.33 [ns]
= 5.47 [μs]
LHSYNC [period:s] = 1/70 [Hz] / (COM + 20 = 260) = 54.95 [μs]
Since SDRAM is auto-refreshed once or less in 5.47 [
μs]:
t
STOP
(ARDMA)
= 2 / f
SYS
[Hz]
= 33.33 [ns]
CPU bus stop rate
= t
STOP
(LDMA ARDMA) [s] / LHSYNC [period:s]
= (5.47 [μs] + 33.33 [ns]) / 54.95 [μs] = 10.01 [%]