MAX6850 MAXIM [Maxim Integrated Products], MAX6850 Datasheet - Page 22

• Manufacturer Part Number: MAX6850
• Description: 4-Wire Interfaced, 7-, 14-, and 16-Segment Alphanumeric Vacuum-Fluorescent Display Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

put latches. In the default condition, VFBLANK is low to
enable its VFD tube driver outputs to follow the state of
the VFD tube driver’s output latches. The VFBLANK out-
put is used for PWM intensity control and to disable the
VFD tube driver in shutdown.
The multiplex engine transmits grid and anode control
data to the external VFD driver using VFCLK, VFDOUT,
and VFLOAD. The number of data bits m transmitted is
set by the user in the shift-limit register (Table 30). Figure
12 is the VFD multiplex timing diagram.
4-Wire Interfaced, 7-, 14-, and 16-Segment Alpha-
numeric Vacuum-Fluorescent Display Controller
Table 26. Grids Register Format
22
Figure 12. VFD Multiplex Timing Diagram
Display has 1 grid: G0 (always)
Display has 2 grids: G0 and G1
Display has 3 grids: G0 to G2
Display has 4 grids: G0 to G3
Display has 45 grids: G0 to G44
Display has 46 grids: G0 to G45
Display has 47 grids: G0 to G46
Display has 48 grids: G0 to G47
VFDOUT
VFLOAD
______________________________________________________________________________________
VFCLK
1.25
µ
100µs TIMESLOT
s
1.25
GRID 0
µ
GRIDS
UP TO
s
1
DD0 DD1 DD2 DD3
µ
s 1
µ
s
Multiplex Architecture
100µs TIMESLOT
GRID 1
DD4 DD5 DD6 DD7 DD8 DD9 DD10
GRID 1's DATA, SENT DURING GRID 0's TIMESLOT
ONE COMPLETE MULTIPLEX CYCLE AROUND N GRIDS (OSC = 4MHz)
100µs TIMESLOT
COMMAND
ADDRESS
GRID N-4
0x03
0x03
0x03
0x03
0x03
0x03
0x03
0x03
0x03
GRID 0's 100µs MULTIPLEX TIMESLOT
100µs TIMESLOT
D7
GRID N-3
0
0
0
0
0
0
0
0
0
The essential rules for multiplex action are as follows:
• The external VFD driver’s data latch contains the
• The VFBLANK input is controlled to provide the
• The VFCLK and VFDOUT outputs are used to fill the
• The VFLOAD output loads the new grid-anode data
D6
data for the current grid being displayed.
PWM intensity control.
external VFD driver’s shift register with the multiplex
data for the next grid, during the multiplex timeslot
for the current grid.
pattern at the start of its multiplex cycle.
M-4
0
0
0
0
0
0
0
0
0
M-3
100µs TIMESLOT
D5
—
0
0
0
0
1
1
1
1
M-2 M-1
GRID N-2
REGISTER DATA
D4
—
0
0
0
0
0
0
0
0
M
D3
—
(M IS VALUE IN SHIFT-LIMIT REGISTER)
100µs TIMESLOT
0
0
0
0
1
1
1
1
GRID N-1
D2
—
0
0
0
0
1
1
1
1
D1
—
0
0
1
1
0
0
1
1
100µs TIMESLOT
GRID 0
D0
—
0
1
0
1
0
1
0
1
START OF NEXT
CYCLE
HEX CODE
0x2C
0x2D
0x00
0x01
0x02
0x03
0x2E
0x2F
—