Fluke Biomedical 945A - Manual (Page 58)

Display Control (Write Only)
Registers U71 and U72 are used to control and display data on the front panel 7-segment displays. Five
digits are used along with two spare digit drive signals. The display control register (U71) is an 8 bit
register, utilizing four data bits (D0-D3). The display data register (U72) is also an 8 bit register utilizing
five data bits (D0-D4). Both U71 and U72 outputs are reset (low) upon initial power-up.
U71 is used to select the digit to be written as well as to set the WRITE bit input to U75, the display
controller. U72 is used to enter the data to be written and a decimal point for the selected digit.
U75 is a universal eight digit 7-segment LED driver controller used with common anode devices.
Address inputs (A0-A2), supplied by U71, are used to select the digit as shown below:
A2 A1 A0 Selects
0 0 0 Digit 1
0 0 1 Digit 2
0 1 0 Digit 3
0 1 1 Digit 4
1 0 0 Digit 5
7 - Segment Front Panel Display
Digit 5 Digit 4 Digit 3 Digit 2 Digit 1
Data inputs D0-D3 and the decimal point, supplied by U72, are used to enter data in the selected digit as
shown in Table 4-18.
Table 4-18. Hex Data (Written to Address 4008)
Hex Data 0 1 2 3 4 5 6 7 8 9 A B C D E F
Display 0 1 2 3 4 5 6 7 8 9 - E H L P (blank)
Character
The display controller contains all necessary circuitry including address decoding, static RAM, and
multiplex oscillator for interdigit blanking.
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