Datasheet

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SBAS203J − MARCH 2002 − REVISED JANUARY 2008
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9
EXPLANATION OF THE AC SYMBOLS
Each Timing Symbol has five characters. The first character is always ‘t’ (= time). The other characters, depending on their positions, indicate the name of a signal
or the logical status of that signal. The designators are:
AAddress
CClock
DInput Data
HLogic Level HIGH
IInstruction (program memory contents)
LLogic Level LOW, or ALE
PPSEN
QOutput Data
RRD
Signal
tTime
VValid
WWR
Signal
XNo Longer a Valid Logic Level
ZFloat
Examples:
(1) t
AVLL
= Time for address valid to ALE LOW.
(2) t
LLPL
= Time for ALE LOW to PSEN LOW.
t
LHLL
t
AVLL
t
LLPL
t
PLPH
t
LLIV
t
LLAX
t
PLAZ
t
PXIZ
t
PXIX
t
AVIV
t
PLIV
A0−A7 A0−A7
A8−A15A8−A15
INSTR IN
ALE
PSEN
PORT 0
PORT 2
Figure 1. External Program Memory Read Cycle
t
AVLL
ALE
RD
PSEN
PORT 0
PORT 2
A0−A7
from RI or DPL
DATA IN A0−A7from PCL INSTR IN
P2.0−P2.7 or A8−A15 from DPH A8−A15 from PCH
t
AVDV
t
LLDV
t
WHLH
t
RLRH
t
LLWL
t
LLAX
t
RLAZ
t
RHDX
t
RLDV
t
AVWL
t
RHDZ
Figure 2. External Data Memory Read Cycle