Parallel Interface - Tektronix 2212 Service Manual

Diagnostic LED's
Digital Circuitry
Switching the different timing signals is performed by multiplexer U1714.
The ROLLCLK signal which is monitored by the statemachine, is derived
from SA VCLK through the mono stable multi vibrator U1701B.
The acquisition ram is not used in roll mode; the data from latches U1603
and U1604 is transferred directly to the microprocessor through the bus
connection U1606 and U1608 while the outputs of the acquisition RAM's are
disabled.
Roll Mode Data Transfer to 68070.
The DMA transfer consists of single word (two bytes) cycle stealing DMA
transfers every 200 microseconds.
The hardware protocol is basically the same as in record mode.
Like indicated in the timebase table, external clocking of the acquisition
speed is also possible. The EXT CLK input on J1700 is converted to the TTL
level EXTCLOCK signal by the circuitry around Q1700 and Q1701 and
U1700. In roll mode the maximum frequency is limited to a little over
4
kHz
by the mono stable multi vibrator U1701A.
The LED's DS2100, DS2101 and DS2102 are added for debugging purposes only.
DS2100 should only be illuminated during power up when the RESET_0 line is
active. During normal operation the DS2101 LED will blink with a cycle time of
exactly 1 second, indicating that the operating system software is active. The
DS2102 LED should blink at a much slower rate (period time 5 to 25 seconds)
indicating that the separate tasks in the software are all active.
Parallel Interface
~
The parallel interface is completely software driven through latches which are
~
connected to the processor bus. The interface lines are basically a Centronics
type implementation.
2212 Service Manual
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