Adding a right shift register

Day 29

     I am considering adding constant and circular shift right to my function set this will mean adding some complexity to the 3-8 decoder as it would then need at least 11 total outputs but adding 1 more bit to the input line will give me up to 16 total instructions so I am thinking on more instructions to add to make this change worth the effort. The constant would add another memory register but could be completely switch operated to save components, more on that Saturday.

     The right shift function itself could be easily called by inserting a pair of relays into the left shift data stream before the shift and when enabled would simply reverse the order of the inputs. If you look at the schematic below it shows how I plan to implement this shift though the tagging makes it somewhat obfuscated. The b register inputs are on the right where they pass through the right shift enable circuit if the circuit is not enabled the NC contacts pass through the inputs in descending order where the most significant bit is shifted to the least significant spot and all others move up 1 place. If the relays are energized the order of inputs is reversed Shifting the least significant bit to the most significant place and all others moving down 1 place. The resulting outputs are placed into the left shift enable where if left shift is enabled then the bits simply pass through, if not the outputs are inverted again to match the data bus order.  After this the resulting output will then have to go through yet another enable circuit that activates for either a left OR a right shift and a simple OR function will be added to the enable circuit to allow this and prevent feedback into the data bus.

     While this circuit adds 5 more relays minimum to the overall design I feel it also adds extra functionality that will save valuable compute cycles and saves the need for yet another data line set in this already large computer. the indicator lights will be placed at the input to the shift enable circuit to save the need for 8 extra lights. There will be either 1 or 2 lights to indicate which shift function is being called. I am as yet unsure if this will be a bi color LED, 2 separate indicators, or 1 indicator that is on for 1 shift or off for the other. That is a style call though so it can wait quite some time. I will be prototyping this circuit up ASAP.

     Parts update, still no sign of anything from china but my capacitors and the first batch of indicators is out for delivery today. I also received shipping notification on the second larger batch of relays I ordered over the weekend so those should be here in a few weeks. I ended up making my purchase decision based on both the size of this order and the resultant per unit cost, fingers crossed it works out because that was quite a few relays. It did manage to get me below $2.50 each relay so I think I may try and do larger batch orders like that from now on.