======================PROTOCOLS_GPIB==============================

IFC                   Interface Clear        controller initialize all devices
REN                   Remote Enable          controller enables remote control
ATN                   Attention              controller placing addr or control
NRFD                  Not ready for data     listener holds down until ready
NDAC                  Not Data Accepted      listener holds down until has data
DAV                   Data valid             Talker holds down says data here  
DIOX                  DIO1_lsb ->DIO8_m      Talker supplies data 
EOI                   End of Identify        Talker says last data 
SRQ                   Service request        any device can interrupt
GPIB                  1 controller           15 devices @ 500kbps
20m                   Max distance           or  number of devices*2meters   
00                    Command Address
20                    Listen Address
40                    Talk Address
60                    Second Address
LF                    10  terminate CR LF
X                     88
CR                    12
Number                Talk   Listen
0                     @      space
1                     A_65   !_33
2                     B      "
3                     C      #
:                     :      :
:                     :      :
31                    _      ?   <= untalk
bus                   is TTL active low ( open collector )  5V at 7mA
0 = false > 2.0v                       ^ 5V                 
1 = true  < 0.8V                      /_\                 
                              ___/\  __|    
                      ___    |     \/ 3.1K
                     |   |___|                   |\
                     |___|   |___________________| \/\____
                             |                   | /\/
                             |___/\  ____        |/
                                   \/   _|_
                              6.2K      ///
                     _
                      |
                      |__________________________________________        ATN   
                      :               ________           ________ 
                      :     TRI STAT |        |         |        |        
                      :    ..........| D1->D8 |.........| D1->D8 |... .   DATA
                      :          .-->|________|     .-->|________|
                      :          :      :     ^     :      :     ^
                      :        __:______v     :_____:______v     :____
                      :       |  :      |     |     :      |     |       DAV
                      :    ___|  :      |_____|     :      |_____|
                      :       ^  :        :   ^     :        :   ^
                      :       :  :________v   :     :________v   :
                      :       :  |        |   :     |        |   :     |  NRFD
                      :     __:__|        |___:_____|        |___:_____|  
                      :       ^           :   :   ^          :   :   ^
                     ___    If both       :   :___:          :   :___:
                        |    low           -->|   |           -->|   |    NDAC
                        |_____v_______________|   |______________|   |___
                             _____________     
GPIB Male                   | |       \   \
                            | |  _____ \   \
                      DIO1  | 1(|  |)_)|13 |  DIO5
                            | | |  |_| |   |  
                      DIO2  | 2(|  |)_)|14 |  DIO6  
                            | | |  |_| |   |  
                      DIO3  | 3(|  |)_)|15 |  DIO7  
                            | | |  |_| |   |  
                      DIO4  | 4(|  |)_)|16 |  DIO8  
                            | | |  |_| |   |  
                      EOI   | 5(|  |)_)|17 |  REN
                            | | |  |_| |   |                  
                      DAV   | 6(|  |)_)|18 |  GND 
                            | | |  |_| |   |                 
                      NRFD  | 7(|  |)_)|19 |  GND  
                            | | |  |_| |   |  
                      NDAC  | 8(|  |)_)|20 |  GND  
                            | | |  |_| |   |  
                      IFC   | 9(|  |)_)|21 |  GND  
                            | | |  |_| |   |  
                      SQ    |10(|  |)_)|22 |  GND  
                            | | |  |_| |   |  
                      ATN   |11(|  |)_)|23 |  GND  
                            | | |  |_| |   |  
                      GND   |12(|  |)_)|24 |  GND Logic 
                            | | |__|_| |   |
                            | |       /   /  
                            |_|______/___/
                             _____________     
GPIB Female                 |         \   \
                            |   _____  \   \
                            |  | _|  |  |   | 
                      GND   |12|)_) (|24|   |  GND Logic  
                            |  | _|  |  |   | 
                      ATN   |11|)_) (|23|   |  GND  
                            |  | _|  |  |   | 
                      SQ    |10|)_) (|22|   |  GND  
                            |  | _|  |  |   | 
                      IFC   | 9|)_) (|21|   |  GND  
                            |  | _|  |  |   | 
                      NDAC  | 8|)_) (|20|   |  GND  
                            |  | _|  |  |   | 
                      NRFD  | 7|)_) (|19|   |  GND  
                            |  | _|  |  |   | 
                      DAV   | 6|)_) (|18|   |  GND  
                            |  | _|  |  |   | 
                      EOI   | 5|)_) (|17|   |  REN  
                            |  | _|  |  |   | 
                      DIO4  | 4|)_) (|16|   |  DIO8  
                            |  | _|  |  |   | 
                      DIO3  | 3|)_) (|15|   |  DIO7  
                            |  | _|  |  |   | 
                      DIO2  | 2|)_) (|14|   |  DIO6  
                            |  | _|  |  |   | 
                      DIO1  | 1|)_) (|13|   |  DIO5  
                            |  |__|__|  /   / 
                            |          /   /  
                            |_________/___/
GPIB                  I/0 INTERFACE (IEEE-488)  HPIB/GPIB/IEEE-488 standard 
                      Up to 15 devices. 
                      GPIB 24 Line Bus 
Pin                   Signal 
Number                Description        Function 
1                     DATA 1/O 1         Dateline 1/O bus 
2                     DATA 1/O 2         Dateline 1/O bus 
3                     DATA 1/O 3         Data line 1/O bus 
4                     DATA 1/O 4         Data line 1/O bus 
5                     EIO                End or identity 
6                     DAV                Dalavalid 
7                     NRFD               Not Ready For Data 
8                     NDAC               Data Not Accepted 
9                     SRQ                Service Request 
10                    IFC                InterfaceClear 
11                    ATN                Attention 
12                    Shield             or wire ground 
13                    DATA 1/O 5         Data line 1/O bus 
14                    DATA 1/O 6         Data line 1/O bus 
15                    DATA 1/O 7         Data line 1/O bus 
16                    DATA 1/O 8         Data line 1/O bus 
17                    REN                Remote Enable 
18                    Ground             Ground 
19                    Ground             Ground 
20                    Ground             Ground 
21                    Ground             Ground 
22                    Ground             Ground 
23                    Ground             Ground 
29                    Logic Ground       Logic Ground             
Devices               can be set up in star, linear or other combinations 
                      using male/female stackable connectors.