Tektronix 492 - Page 160

Maintenance—492/492Ρ Service Vol. 1 (SN B030000 & up)
Z-Axis/RF Interface (refer to diagram 27). A register on
the Z-Axis/RF Interface board enables Z-axis and RF
attenuator control (see Table 4-9).
Crt Readout (refer to diagram 29). One register (5F)
controls crt readout and data steering. Another register (2F)
accepts data from the microcomputer (see Table 4-10).
Table 4-9
Z-AXIS AND RF DECK CONTROL (4F)
Table 4-10
CRT READOUT REGISTERS (5F AND 2F)
Bit
Function
DB7 Baseline clipper on/off (1/0)
DB6
DB2
DBO
RF attenuation
1
1 1
OdB
1
1
0
10 dB
0 1 1 20 dB
1
0 1 30 dB
1
0 0
40 dB
0
0
1
50 dB
1
1 1 60 dB
DB5
1 = 829 MHz 2nd Converter
0 = 2 GHz 2nd Converter
DB4 1 = EXT MIXER
0 = RF INPUT
DB3 Set to 0 for 100 ms to switch
attenuator
Bit Function
Crt Control (5F)
DB3 1 = max span dot
0 = center frequency dot
DB2 1 = error or GPIB RDOUT message
(page 2)
0 = normal readout (page 1)
DB1
1 = data sent to 2F is character address
0 = data sent to 2F is character code
DBO 1 = readout on
0 = readout off—required to load
characters
Address/Data (2F)
DB1
in 5F = 1
DB6—DBO Address in readout RAM. Upper line is
0—31. Lower line is 32—63 (page of
RAM selected by DB2 at address 5F)
DB1
in 5F = 0
DB7
1 blanks character (used for space)
DB6 1 shifts character down 112 screen (used
for upper readout only)
DB5—DBO
Lower 6 bits of ASCII code for character
J
REV JUN 1983
4-47