Specifications

Interrupt Configuration

Since the above setup requires an autovector, we need to program the autovector register so that the vector number is

generated internally when an interrupt is acknowledged. In the above case, we are using interrupt level three, therefore

$08 should be stored in the autovector register.

The vector table should also be modified to point to the new interrupt handler. For interrupt level three, the vector is

stored at location $06C. The value contained at this memory location should be modified to contain the address of the

new interrupt handler.

DMA Channel Configuration

In order to use DMA, the DMA channel must be configured for single address, burst mode, and external request

generation. On GPIB reads, the TNT4882 will assert its DRQ signal if the FIFOs contain a byte that needs to be

transferred to memory. On GPIB writes, the TNT4882 will assert its DRQ signal when the FIFOs are not full.

For every system there is a point where programmed I/O is faster than DMA I/O and vice versa. Programmed I/O is

usually faster for small transfer sizes (500 bytes or less). It is recommended that you determine the crossover point and

then use it as a switch to decide when to use programmed I/O or DMA.

Device Level Programs

We recommend using the TNT4882 in one-chip mode. The TNT4882 by default powers up in two-chip mode to

maintain backwards compatibility. Therefore, it is important to initialize the TNT4882 so that it is in one-chip mode.

Follow the steps listed in the GPIB ESP-488TL Software Reference Manual for TNT4882. The manual also includes

sample routines that can help you write programs for the TNT4882.

Hardware Interface Test

A hardware interface test and library is included with this package. Before you use the hardware test, make any

changes if necessary to the header files and re-compile the program. We used Microtec Research Software

Development Tools, version 4.2D for DOS and an M68340EVS System. The header files include information such as

the base address where the TNT4882 is located. The hardware interface test program tests the interface between

MC68340 and TNT4882. It performs three different types of I/O:

• Programmed I/O

• Interrupt Driven I/O

•DMA I/O

To perform the hardware test, download the HARDWARE.ABS file on the MC68340EVS system. The HARD-

WARE.ABS file is in the HARDWARE directory.