Datasheet

ADuC841/ADuC842/ADuC843
Rev. 0 | Page 78 of 88
TIMING SPECIFICATIONS
1, 2, 3
Table 41. AV
DD
=2.7 V to 3.6 V or 4.75 V to 5.25 V, DV
DD
= 2.7 V to 3.6 V or 4.75 V to 5.25 V; all specifications T
MIN
to T
MAX
,
unless otherwise noted
Parameter 32.768 kHz External Crystal
ADuC842/ADuC843 CLOCK INPUT (External Clock Driven XTAL1) Min Typ Max Unit
t
CK
XTAL1 Period 30.52 µs
t
CKL
XTAL1 Width Low 6.26 µs
t
CKH
XTAL1 Width High 6.26 µs
t
CKR
XTAL1 Rise Time 9 ns
t
CKF
XTAL1 Fall Time 9 ns
1/t
CORE
ADuC842/ADuC843 Core Clock Frequency
4
0.131 16.78 MHz
t
CORE
ADuC842/ADuC843 Core Clock Period
5
0.476 µs
t
CYC
ADuC842/ADuC843 Machine Cycle Time
6
0.059 0.476 7.63 µs
1
AC inputs during testing are driven at DV
DD
– 0.5 V for a Logic 1 and 0.45 V for Logic 0. Timing measurements are made at V
IH
min for Logic 1 and V
IL
max for Logic 0, as
shown in Figure 87.
2
For timing purposes, a port pin is no longer floating when a 100 mV change from load voltage occurs. A port pin begins to float when a 100 mV change from the
loaded V
OH
/V
OL
level occurs, as shown in Figure 87.
3
C
LOAD
for all outputs = 80 pF, unless otherwise noted.
4
ADuC842/ADuC843 internal PLL locks onto a multiple (512 times) of the 32.768 kHz external crystal frequency to provide a stable 16.78 MHz internal clock for the
system. The core can operate at this frequency or at a binary submultiple called Core_Clk, selected via the PLLCON SFR.
5
This number is measured at the default Core_Clk operating frequency of 2.09 MHz.
6
ADuC842/ADuC843 machine cycle time is nominally defined as 1/Core_CLK.
Parameter Variable External Crystal
ADuC841 CLOCK INPUT (External Clock Driven XTAL1) Min Typ Max Unit
t
CK
XTAL1 Period 62.5 1000 ns
t
CKL
XTAL1 Width Low 20 ns
t
CKH
XTAL1 Width High 20 ns
t
CKR
XTAL1 Rise Time 20 ns
t
CKF
XTAL1 Fall Time 20 ns
1/t
CORE
ADuC841 Core Clock Frequency 0.131 20 MHz
t
CORE
ADuC841 Core Clock Period 0.476 µs
t
CYC
ADuC841 Machine Cycle Time 0.05 0.476 7.63 µs
t
CKH
t
CKL
t
CK
t
CKF
t
CKR
03260-0-085
Figure 86. XTAL1 Input
DV
DD
– 0.5V
0.45V
0.2DV
DD
+ 0.9V
TEST POINTS
0.2DV
DD
– 0.1V
V
LOAD
– 0.1V
V
LOAD
V
LOAD
+ 0.1V
TIMING
REFERENCE
POINTS
V
LOAD
– 0.1V
V
LOAD
V
LOAD
– 0.1V
03260-0-086
Figure 87. Timing Waveform Characteristics