User manual

VETTA Theory of Operation………………Line 6 confidential ……………………………. Page 17 of 18
U.I. LEDs:
All of the U.I. LEDs (except the LCD’s backlight LEDs) are multiplexed in a 15 row by 5-
column matrix. The rows of the matrix are driven by U4, U3 and the associated 16 buffer
transistors. The columns of the matrix are directly driven by U9. The multiplexing cycle is
about 10ms long. The matrix driver circuit resides on the Left U.I. PCB (page 3 of 3 of left U.I.
PCB).
U.I. Switches and encoders:
All of the U.I. switches are read in a 5 by 7 matrix. One side of the matrix is driven by U5, and
the other by U7 (page 2 of 3 of left U.I. PCB). The encoders, except E8 (program select), are
read in a 12 by 2 matrix driven by U6 and U4. E8 is read directly by U6. Notice that the
encoders are 24 positions except for E9 (amp select) and E14 (Page).
U.I. LCDs:
Both LCD modules are written to and read from through the U.I. PCB parallel bus FP_D[0:7].
Their electronic is supplied with the +5V. Their backlight LED are also supplied from the 5V
through current limiting resitors, R46 for the graphic LCD and R12 for the Character LCD.