Diamond Systems 16-Channel 12-Bit Analog Output PC/104 Module Output Operations, Input Operations

Operating Modes

Mode 2 (Strobed Bi-Directional Bus I/O)

The functional configuration provides a means for communi- cating with a peripheral device or structure on a single 8-bit bus for both transmitting and receiving data (bi-directional bus I/O). “Hand shaking” signals are provided to maintain proper bus flow discipline similar to Mode 1. Interrupt gener- ation and enable/disable functions are also available.

Mode 2 Basic Functional Definitions:

•Used in Group A only

•One 8-bit, bi-directional bus Port (Port A) and a 5-bit control Port (Port C)

•Both inputs and outputs are latched

•The 5-bit control port (Port C) is used for control and status for the 8-bit, bi-directional bus port (Port A)

Bi-Directional Bus I/O Control Signal Definition

(Figures 11, 12, 13, 14)

INTR - (Interrupt Request). A high on this output can be used to interrupt the CPU for both input or output operations.

Output Operations

OBF - (Output Buffer Full). The OBF output will go “low” to indicate that the CPU has written data out to port A.

ACK - (Acknowledge). A “low” on this input enables the three-state output buffer of port A to send out the data. Oth- erwise, the output buffer will be in the high impedance state.

INTE 1 - (The INTE flip-flop associated with OBF). Con- trolled by bit set/reset of PC4.

Input Operations

STB - (Strobe Input). A “low” on this input loads data into the input latch.

IBF - (Input Buffer Full F/F). A “high” on this output indicates that data has been loaded into the input latch.

INTE 2 - (The INTE flip-flop associated with IBF). Controlled by bit set/reset of PC4.