Keithley 2010, Руководство по обслуживанию

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Memory circuits
ROMs U156 and U157 store the firmware code for instrument operation. U157 stores the
D0-D7 bits of each data word, and U156 stores the D8-D15 bits.
RAMs U151 and U152 provide temporary operating storage. U152 stores the D0-D7 bits of
each data word, and U151 stores the D8-D15 bits.
Semi-permanent storage facilities include NVRAM U136. This IC stores such information as
instrument setup and calibration constants. Data transmission from this device is performed
serially.
RS-232 interface
Serial data transmission and reception is performed by the TXDB and RXDB lines of the
MPU. U159 provides the necessary voltage level conversion for the RS-232 interface port.
IEEE-488 interface
U158, U160, and U161 make up the IEEE-488 interface. U158, a 9914A GPIA, takes care of
routine bus overhead such as handshaking, while U160 and U161 provide the necessary
buffering and drive capabilities.
Analog
Circuitry
(See Figure 4-3)
NVRAM
U136
ROM
U156, U157
RAM
U151, U152
XADTX
XADCLK
XADTS
XADRX
O
P
T
O
I
S
O
ADTX
ADCLK
ADTS
ADRXB
68306
µ
P
U135
Scan Control
Keypad
Display Board
Controller
Display
DS401
XTAL
Y101
Trigger
U146, U164
Trigger
Link
TRIG IN
TRIG OUT
AT101
U150
U155
IN
OUT
RS-232
U159
Data IN
Data OUT
GPIB
RS-232
Port
IEEE-488
Bus
U158, U160,
U161
U401
Figure 4-2
Digital circuitry block
diagram
Troubleshooting 4-7