Ok I have done some double triple checking in the doc TM 11-5841-281-12 and it seams that the three displays are interdependent. Refresh is now almost cake! Well while writing this I realized that I the selected display character needs a LAMP TEST, and CURSOR (blinking) seems like a place for a 555. BTW including the CURSOR and a LAMP TEST functions ruled out using the MCP23S17 so I pivoted to use 74HC595 all the way around except for TARGETING which will still use the MCP23S17.
I will now describe the three displays:
- LEFT DISPLAY: Requires two Sixteen Segment Alphanumeric Displays and four Seven Segment Displays which requires 8 x 74HCT595 shift registers.
- RIGHT DISPLAY: Requires one Sixteen Segment Alphanumeric Display and six Seven Segment Displays which requires 8 x 74HCT595 shift registers.
- CENTER DISPLAY: Requires two Seven Segment Displays and one Sixteen Segment Alphanumeric Display which requires 4 x 74HCT595 shift registers.
- TARGET, COLONS. and LEDs: Requires one Seven Segment Display, 4 Colon Displays and several LEDs and some BJT's.
LEFT DISPLAY 
RIGHT DISPLAY 
CENTER DISPLAY 
TARGET ETC 
Also required are keep alive resistors on all the segments. Also required at two additional requirement I have to have a blinking cursor, on the Sixteen Segments Displays I need to drive segments B & A, for the Seven Segment Displays I need to drive one segments D. For blinking a NE555 should suffice. and to make maters worse I might have to add tri-state drivers between the Display unit and the shift register to control the outputs.
The Cursor is under control of the decoder which is 0 - 17 which is driven via 3 x 74LS138(s) 3 input decoders, this will be driven by the Arduino. I think that I can drive all three displays from one clock to drive Left, Right and Center displays. The other two signals required are latch, and data which can be tri-stated between the three displays which will take 3 bits: 0, latch, data.
WOOPEE!! NO MORE BJTs!!!! I just discovered a part from TI
TPIC6C595 which is a drop in replacement for the 74HC595 but it can put out 100 ma drain per segment but only has a total output budget of 250 ma but my Pinlites are 15+/-2ma so even they drew 20 ma each times eight segments would only be 160 ma power required which is well inside the budget! 27Jan25
REVISIONS:
- 27 Jan 2025 Add the paragraph woopee!!....
- 28 Jan 2025 Rewrote and restructured the first paragraph. starting with OK
- Side Note: by using the 74HC595 with the TPIC6C595 it will raise the cost of my components as they run about $1.00 each or so.
