The Central Processing Unit (CPU) is the central intelligence of the Attache system. The CPU’s address and data lines form a system bus. This system bus provides the means for the logic sections, hardware modules, and peripheral devices to interface.

The Direct Memory Access controller (DMA) operates in parallel with the CPU. The DMA handles data transfers between memory locations and Input/Output (I/O) devices by taking control of the system bus. Either the DMA or the CPU controls the system bus at any given time.

An I/O selector identifies the I/O device which interfaces with the processor.

An Erasable Programmable Read-Only Memory (EPROM) chip loads the bootstrap routine into Random Access Memory (RAM). The bootstrap routine is the program which starts up the system. The EPROM is then disabled, which allovls RAM to be accessed. The EPROM contains the Terminal Emulation routine, the Monitor Mode, system diagnostics, and pointers to the diskette location to load the Control Program for Microcomputers (CP/M) operating system.

An Expansion Connector allows a variety of external devices to interface with the Attache system via the system bus.

The memory block represents 64K bytes of Random Access Memory (RAM). Attache uses Dynamic RAM, which requires refreshing. These refreshes are timed by Row Address S~robe/Column Address Strobe (RAS/CAS). Virtual mapping allows software to relocate any 8K byte memory region to any other memory region.

Attache’s 23 KHz switching power supply powers all the system modules. The Power Okay signal ensures power is properly stabilized before the processor is initialized.

Two ports allow periphe~al devices to communicate with the system via the Ser ial Input/Output controller (SIO).

A Counter Timer Controller (CTC) generates two clock signals which produce baud rates for the ports. Additionally, two CTC channels are used in the 60 Hz Interrupt Routine and Floppy Interrupt Routine process.

The display logic contains a CRT controller which synchronizes the video signals and addresses data transfers between the· display and the processor. The display constantly reads information from the display memory as it refreshes the screen. The CPU updates the display memory as display data changes.
Display memory is 4K bytes of alphanumeric RAM and 10K bytes of graphic RAM. The alphanumeric data is combined with the attributes and a character generator EPROM outputs the data bits which comprise ·the ASCII characters. The data is then shifted to the display module. Data is read back from the display memory to the processor through the same logic paths.

The floppy controller writes or reads data from the diskette. Data and clock information are written on the same diskette track. Clock pulses are separated from the data by a data separator as data is read back to the processor. Write precompensation ensures that data is written at the correct diskette location.

A Parallel Input/Output controller (PIO) allows additional de~ices to interface with the system bus without increasing the capacitive load on the bus.

The devices which connect to the PIO are:

• the Real-Time Clock (RTC), which performs time of day functions,
• Complementary Metal-Oxide Semiconductor Random Access Memory (CMOS RAM), which stores system parameters
• a sound synthesizer, which provides keyboard feedback and is software programmable for other sounds,
• a control latch that controls CRT brightness, generates EPROM enable, controls the floppy motor, and generates graphic enable, and
• the keyboard, which provides system reset control, data input, and control input.

To run the Otrona Attache in Microsoft DOS mode, the computer must be equipped with the 8086 module.

Attache 8:16 provides IBM-PC compatibility in the following ways:

Operating System – Attache 8:16’s enhanced version of Microsoft’s MS-DOS 2.0 is fully compatible with the IBM PC-DOS 2.0.
The differences between IBM’s PC-DOS and the Microsoft „generic” MS-DOS result from the IBM PC’s physical and logical architecture.
Many operations that would normally be handled by the operating system (such as logical input/output instructions) are reduced to microcode instructions in the PC’s ROM.
Since IBM’s ROM is proprietary, Attache’S MS-DOS handles these functions in the portion of the operating system known as the BIOS (Basic Input Output System). This section of MS-DOS (IO.SYS) has been customized for Attache 8:16 to emUlate the PC’s microcode.
Attache 8:l6’s BIOS for MS-DOS is completely PC-compatible.
Any program written for the PC that performs all input/output operations through IO.SYS will run without modification. For programs that are written to the IBM ROM rather than the BIOS, Attache 8:l6’s BIOS emUlates PC I/O port routines. This allows Attache 8:16 to run most applications software that is written for the IBM-PC.
Diskettes – Attache 8:16 reads and writes disks in the same format as the PC, so data disks can be freely exchanged between the two machines.
You cannot actually boot a PC-DOS operating system diskette on Attache 8:16, but you can insert the disk and run the programs after you have loaded MS-DOS from the Attache DOS diskette.

As an 8-bit computer, the 8:16 uses a Z-80A processor and 64K bytes of RAM with the CP/M operating system.
CP/M and MS-DOS cannot be run simultaneously.
Either system is selected automatically by simply loading the appropriate software. If a disk containing MS-DOS is loaded, the computer is in l6-bit mode running MS-DOS.
If a disk containing CP/M is loaded, the computer is in 8-bit mode running CP/M.
Attache 8:16 automatically configures the keyboard, disk format, graphics format, and input/output structure for the selected mode of operation each time a system is loaded.

Below is an example of booting the CP/M system on the Otrona Attache computer.