Carl C. Hoffchoff@cs.wrigth.edu
> My Pro380 cable (bcc03-o6) won't work with RB, what's wrong?
> The pin orders seemed to be quite the same.
The Rainbow uses a BCC17 cable with the VR241 color monitor, not the BCC03 cable used by the Professional, DECmate and VT241 terminal. Here in the United States, Digital Equipment Corporation (DEC) is [was] selling the BCC17-6 cable for $56 US.
The following data was extracted from the PDP-11 Systems And Options Catalog, October - December 1984 (DEC part number ED-26049-41), page 4-19.
The cables consist of three 30 AWG coax cables and four 20-AWG stranded conductors with a 38 AWG tinned copper braid shield. The connectors are:
P1 15 position D subminiature P2 keyboard plug P3 "B" BNC P4 "G" BNC P5 "R" BNC
The wiring is:
P1-1 P3 coax shield P1-2 P4 coax shield P1-3 P5 coax shield P1-4 -------------- P1-5 P1-13 jumper P1-6 P2-3 conductor P1-7 -------------- P1-8 P2-2 conductor P1-9 P3 coax center P1-10 P4 coax center in BCC03 only -- nothing in BCC17 P1-11 P5 coax center P1-12 P4 coax center in BCC17 only -- nothing in BCC03 P1-13 P1-5 jumper P1-14 P2-1 conductor P1-15 P2-4 conductor
The following pin assignments for the Rainbow keyboard/monitor connector were extracted from "PC100 Mother Board" skematic (DEC drawing size D, code CS, number 5415486-0-1, revision E) which is included in the "PC100 Field Maintenace Print Set (DEC part number MP-01491-00). The assignments are also listed in the Rainbow 100 Technical Manual (DEC part number EK-PC100-TM-001), table 3-6 on page 3-22 except that table shows the keyboard data flowing in directions opposite that shown on the skematic and listed below.
The BCC02 monochrome cable wiring was obtained by inspecting that cable. BCC03 and BCC17 cable wiring was from the source listed above.
Rainbow Pin BCC02
MonoBCC03
ColorBCC17
ColorPossible
Dual MonitorRed shield ground 1 - X X Color Green shield ground 2 - X X Color Blue shield ground 3 - X X Color Mono shield ground 4 X - - Monochrome Ground 5 X jumper jumper Monochrome Ground 6 X X X Keyboard +12 volts 7 X - - Monochrome +12 volts 8 X X X Keyboard Blue video 9 - X X Color Green video 10 - X - Color Red video 11 - X X Color Mono video 12 X - X Monochrome - not used - 13 - jumper jumper - Data from keyboard to CPU 14 X X X Keyboard Data from CPU to keyboard 15 X X X Keyboard
Comparison of the above data suggests that when the graphics board is in a Rainbow, the BCC03 cable should route the color graphics signals to the VR241 monitor. However, the monochrome signal generated on the Rainbow's motherboard will not be capable of being displayed with the BCC03 cable.
As indicated in the "Rainbow Color/Graphics Option Programmer's Reference Guide" (DEC part number AA-AE36A-TV), the Rainbow can support three different monitor configurations:
Each of the single monitor configurations presents a problem, that is how to get graphics video data to the monochrome monitor, and how to get motherboard video data to the color monitor. DEC solved these problems with a electronic switch on the motherboard. That switch is controlled by bit 2 of port 0A hexidecimal. Setting that bit to 0 places motherboard video data on pin 12 of the BCC02 / BCC17 cable. In contrast, setting the bit to 1 puts graphics option "green" data on that pin.
To my knowledge, DEC never sold a cable to support the Rainbow's dual monitor configuration. However, some people have built such a cable.
(Note: The above data suggests a Professional or DECmate, when equipped with its graphics option and an appropriate cable, may also be capable of supporting a dual monitor configuration.)
Carl C. Hoff
choff@cs.wrigth.edu