Table 3-3: Timebase Table - Tektronix 2212 Service Manual

Digital Circuitry
Roll Mode Acquisition
Acquiring Roll Mode Data
The roll mode acquisition is created in a different way. Basically, always
at a 4 kHz rate, single acquisitions are taken and transferred
immediately to the microprocessor. The software will then determine the
roll mode acquisition speed and will take care of the way the roll mode
is displayed. The control of this process is again done by the state
machine U1610 and U1611.
Like all other acquisition timing, also the 4 kHz frequency of SAVCLK is
generated by the programmable counters U1710, U1711, U1712 and
U1713.
The relation between the outputs of the microprocessor controlled
latches Ul 705 and Ul 706 and the timing is described in the Timebase
Table (see Table 3-3).
Table 3-3: Timebase Table
SEC/DIV DEC4_0 DEC3_0 DEC2_0 DECtB_0 DECtA_0
so
St ROLL CONV SAV
CLK CLK
20 µs
1 0 0
1
1
1
0 0 20MHz 20MHz
50µs
1
0
0
1
1 0 1 0 8MHz 8MHz
0.1 ms
1 1 1
0
1 1
1
0 8MHz 4MHz
0.2ms
1 1 1 1
0
1
1
0
8MHz 2MHz
0.5ms
1 1 1
0 0
1 1
0 8MHz 800 kHz
1 ms
1 1
0
0
1 1
1 0
8MHz
400 kHz
2 ms 1
1
0 1 0
1
1
0
8MHz
200 kHz
5ms
1
1
0 0 0
1
1
0
8MHz
BO
kHz
l0ms
1
0 0 0
1 1 1
0 8MHz 40kHz
20ms
1
0 0
1
0
1
1 0 8MHz 20 kHz
50ms
1
0 0 0 0
1
1 0 8MHz 8kHz
0.1 s 0 0 0 0
1
1 1
1
8MHz 4 kHz
0.2 s 0 0 0 0
1
1 1 1 8MHz 4kHz
0.5 s 0 0 0 0 1
1
1
1
8MHz 4kHz
ls 0 0 0 0
1
1
1
1
8MHz 4kHz
2s 0 0 0 0
1
1
1
1
8MHz 4 kHz
5s 0 0 0
0
1 1 1 1
8MHz 4kHz
10 s 0
0 0
0
1 1
1
1
8MHz 4kHz
20 s 0 0 0 0
1 1 1 1
8MHz 4kHz
50 s 0
0 0
0
1
1 1 1 8MHz 4 kHz
EXT REC
X X X X X
0 0
0
EXT EXT
EXTROL
X X X X X
0 0
1
EXT EXT
3- 28 Theory of Operation