STD Bus is a computer bus popular with industrial control applications but has also been used in computing applications. The STD Bus has been called "STD-80" as well: this has created a popular confusion that the bus contains 80 pins; however, it refers to its bus being related to the Zilog Z80

Zilog Z80

The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...

 series processors in practical use. The STD Bus stands for "Simple to Design", not "Standard", which is also another common confusion.

General Description

The STD Bus uses 6.5" by 4.5" cards with an edge connector

Edge connector

An edge connector is the portion of a printed circuit board consisting of traces leading to the edge of the board that are intended to plug into a matching socket. The edge connector is a money-saving device because it only requires a single discrete female connector , and they also tend to be...

with 56 pins. There are many different types of STD cards, from processing cards, RAM cards, I/O cards and specialized cards for various applications. There are prototyping cards available from Vector Electronics, and many PCB companies will produce cards with the proper edge connector.

The STD bus, although suffering a decline in use, as evident from the over 100 manufacturers of components in its peak, down to under a dozen today, is still used by hobbyists, manufacturers and in industrial applications.

One application which made a STD bus system more adaptable the then current computers of the mid-80s is the ability to use servo control cards along with a fully programmable computer to be used for mathematical work. One mention of this is the article written by Russell M. Genet and Douglass J. Sauer on the application of computers for astrophysics. In the article, it is mentioned that due to the then large industrial base of cards to control the observatory, and the systems expandability they are more desirable for use in a photometry lab to control the telescope as well as do the data logging and computations required.

STD Bus Configuration

The STD Bus has a card edge connector of 56 pins. The pin configuration is as follows (Flow is relative using a STD Bus Processor Card).

Pin	Mnemonic	Signal Flow	Description	Pin	Mnemonic	Signal Flow	Description
1	+5V	In	Logic Power	2	+5V	In	Logic Power
3	GND	In	Logic Ground	4	GND	In	Logic Ground
5	-5V	In	Negative Logic Power	6	-5V	In	Negative Logic Power
7	D3	In/Out	Data Bus	8	D7	In/Out	Data Bus
9	D2	In/Out	Data Bus	10	D6	In/Out	Data Bus
11	D1	In/Out	Data Bus	12	D5	In/Out	Data Bus
13	D0	In/Out	Data Bus	14	D4	In/Out	Data Bus
15	A7	Out	Address Bus	16	A15	Out	Address Bus
17	A6	Out	Address Bus	18	A14	Out	Address Bus
19	A5	Out	Address Bus	20	A13	Out	Address Bus
21	A4	Out	Address Bus	22	A12	Out	Address Bus
23	A3	Out	Address Bus	24	A11	Out	Address Bus
25	A2	Out	Address Bus	26	A10	Out	Address Bus
27	A1	Out	Address Bus	28	A9	Out	Address Bus
29	A0	Out	Address Bus	30	A8	Out	Address Bus
31	WR	Out	Write to Memory or I/O	32	RD	Out	Read to Memory or I/O
33	IORQ	Out	I/O Address Select	34	MEMRQ	Out	Memory Address Select
35	IOEX	Out	I/O Expansion	36	MEMEX	Out	Memory Expansion
37	REFRESH	Out	Refresh Timing	38	MCSYNC	Out	CPU Machine Cycle Sync
39	STATUS 1	Out	CPU Status	40	STATUS 0	Out	CPU Status
41	BUSAK	Out	Bus Acknowledge	42	BUSRQ	In	Bus Request
43	INTAK	Out	Interrupt Acknowledge	44	INTRQ	In	Interrupt Request
45	WAITRQ	In	Wait Request	46	NMIRQ	In	Non-Maskable Interrupt
47	SYSRESET	Out	System Reset	48	PBRESET	In	Push Button Reset
49	CLK	Out	Clock from Processor	50	CNTRL	In	Aux Timing
51	PCO	Out	Priority Chain Out	52	PCI	In	Priority Chain In
53	AUX GND	In	AUX Ground	54	AUX GND	In	AUX Ground
55	AUX +12V	In	AUX Positive	56	AUX -12V	In	AUX Negative

STD-32

The STD-32 is a pin compatible STD interface that allows the co-existence of both 8-bit and 32-bit systems on a single bus. This is accomplished by the addition of pins between the normal pins that do not connect, nor do they interfere with the original specification. This allows with the proper STD-32 backplane the ability to run legacy cards used for specific applications on the same bus without having to upgrade the complete system.

External links

• Controlled - STD Bus Controlled Systems