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boards:ecb:cvdu:start [2016/07/06 13:50]
boards:ecb:cvdu:start [2016/07/06 19:36] (current)
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 ====== ECB Color Video Display Unit ====== ====== ECB Color Video Display Unit ======
 ===== Introduction ===== ===== Introduction =====
 The ECB Color Video Display Unit board provides a color video terminal to RBC ECB bus systems using the MOS8563 chip found in the Commodore 128. Features include: The ECB Color Video Display Unit board provides a color video terminal to RBC ECB bus systems using the MOS8563 chip found in the Commodore 128. Features include:
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 {{:​boards:​ecb:​cvdu:​colorvdu2.lst|KiCAD eeschema Parts List}} {{:​boards:​ecb:​cvdu:​colorvdu2.lst|KiCAD eeschema Parts List}}
-==== Construction Notes ====+==== Construction Notes for the Color VDU Rev 1.00 / 2.00 ==== 
 +**Rev 2.00 board builders - Notes 1, 2, 3/9, 4, 7 apply to your boards** 
 +''​1. ​ CAUTION: ​ capacitor C15 on the PC layout looks like any other decoupling cap; it is not!!! ​ It is 10pf.\\ 
 +2.  The DRAM chips are decoupled on the schematic using0.22uf caps, about twice the value for the other decoupling caps.  Instead of C11 & C12, which decouple the DRAM chips, the board layout requires that three caps decouple the DRAM chips: ​ C6, C12, & C14.  Use the higher value caps in these three locations.\\ 
 +3.  The resistor network used to convert the output of the 8563 to VGA levels is highly experimental;​ THE VALUES OF THESE RESISTORS MAY CHANGE. ​ I suggest putting a 14-pin socket in the location for R21,​R22,​R23;​R31,​R32,​R33,​R34. (See Note 9, below. ​ These values test okay.)\\ 
 +4.  The schematic from which this board was derived did not specify a value for the inductor on the power supply of the 16Mhz oscillator. ​ Choose one with low series resistance. ​ 1uh to 100uh would be my guess as to the proper inductance. ​ One wants a high frequency choke to isolate the board power supply from oscillator feedback. (I hope the 8Mhz oscillator does not show up on the video chip output.)\\ 
 +Added 23-Jan-2012:​\\ 
 +5.  For version 1.0 ONLY, there is a clearance issue between the 16Mhz oscillator and the nearby 74LS06 if a full-can oscillator is used.  Either switch to a half-can oscillator or bend the pins on the full-can oscillator slightly to avoid shorting pins 14, 13, and 12 of the 74LS06. ​ It would be good to insert an insulator 
 +between the full-can and those pins.  This clearance problem was corrected in version 2.0.\\ 
 +Added 06-Feb-2012\\ 
 +6.  For version 1.0 ONLY, circuit mods are requited to operate with both the SBC v2 (Z80) and the SBC-188. ​ 8563 pin 9 is changed from /WR to RD. RD is generated through an LS04 from /RD output from the LS244. [Pin 9 will have to be disconnected from the board by bending it up and connecting directly to it.  The board surgery needed is too extensive. ​ 20-Feb] 8563 pin 4 is changed from A1 to the output from an added LS00 gate, the inputs to which are /RD and /WR.  Hence, the 8563 will select only during /RD or /WR.  [Pin 4 may be disconnected from the board by bending like pin 9, or by cutting the single trace on the bottom of the board which connects to it.  20-Feb] NO circuit mods are required for version 2.0.\\ 
 +7.  Test programs are posted for the SBC-188 as of this date.\\ 
 +Added 20-Feb-2012\\ 
 +8.  For version 1.0 ONLY, including Dan's comment: ​ U33 pins 2 & 3 must be changed from Vcc to GND.  It is practically impossible to do the surgery on the board, so bend the 2 LS138 pins up and add a jumper to GND (pin 7).  This change is NOT required on version 2.0.\\ 
 +9.  The resistor net which converts 8563 output to VGA levels uses 820 ohm and 390 ohm resistors. ​ For input to a true 75 ohm VGA connector, these appear to be the correct values. (Update to Note 3, above.)\\ 
 +10.  Notes 3 & 6 updated.\\ 
 +Added 14-Dec-2012\\ 
 +11.  For version 1.0 ONLY, the interrupt signal from the keyboard/​mouse is a positive signal, not an inverted signal (/​INT). ​ Hence 74LS04 inverter U21B should be omitted. ​ Bend pin 4 up to disconnect, and solder a jumper from pin 3 to pin 4.  This change is NOT required for version 2.0.\\ 
 +--John Coffman\\ 
 +--Wayne Warthen\\ 
boards/ecb/cvdu/start.1467827433.txt.gz · Last modified: 2016/07/06 13:50 by admin
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