SDA5252 SIEMENS [Siemens Semiconductor Group], SDA5252 Datasheet - Page 75

• Manufacturer Part Number: SDA5252
• Description: TVTEXT 8-Bit Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Table 19
Instruction
External interrupt generated immediately
before (best) / after (worst) the pin is
sampled (time until end of bus cycle).
Current or next instruction finishes in
12-[6-] oscillator periods
Next instruction is MUL or DIV
Internal latency for hardware subroutine
call
Note: values without brackets apply for CDC = 1 and values in brackets for CDC = 0
(see Chapter “Advanced Function Register” on page 115).
If an interrupt of equal or higher priority level is already in progress, the additional wait
time obviously depends on the nature of the other interrupt's service routine.
6.3.5
Processor initialization is accomplished with activation of the RST pin, which is the input
to a Schmitt Trigger. To reset the processor, this pin should be held low for at least four
machine cycles, while the oscillator is running stable. Upon powering up, RST should be
held low for at least 10 ms after the power supply stabilizes to allow the oscillator to
stabilize. Crystal operation below 6 MHz will increase the time necessary to hold RST
low. Two machine cycles after receiving of RST, the processor ceases from instruction
execution and remains dormant for the duration of the pulse. The high-going transition
then initiates a sequence which requires approximately one machine cycle to execute
before normal operation commences with the instruction at absolute location 0000
Program memory locations 0000
routine of the microcomputer. This sequence ends with registers initialized as shown in
Chapter “Memory Organization” on page 49.
After the processor is reset, all ports are written with one (1). Outputs are undefined until
the reset period is complete.
An automatic reset can be obtained when V
V
and the oscillator start-up time does not exceed 10 milliseconds. When power comes on,
the current drawn by RST-pin starts to charge the capacitor. The voltage V
is the capacitor voltage, and increases to V
Semiconductor Group
SS
through a 10 F capacitor, providing the V
Processor Reset and Initialization
H
through 0002
75
Time (Oscillator Periods)
Best Case
2 +
12
don’t care
24
38
DD
DD
DD
is turned on by connecting the RST-pin to
as the capacitor charges. The larger the
rise time does not exceed a millisecond
H
are reserved for the initialization
[6]
[12]
[19]
1 +
Worst Case
2 –
12
48
24
86
RST
SDA 525x
at RST-pin
1998-04-08
[6]
[24]
[12]
[43]
1 –
H
.