The EPROM+ programming system supports the entire Motorola 68HC11 family of microcontrollers. Several variations are shown in the photo. Support is provided with an Asynchronous Communication Adapter; #ACOM1 or #ACOM2. The ASYNC adapter is a complete serial communications subsystem which snaps into the socket on the EPROM+ programming unit. Using the ASYNC adapter, the EPROM+ system connects to the 68HC11 processor via it's Serial Communications Interface (SCI) pins. Once connected, communication is established and a special control program is uploaded into the internal RAM of the processor. With the control program in place, communications is established with the EPROM+ system which provides the user with complete access to specific memory areas (EPROM, EEPROM) or the entire 64K address range of the part ( including I/O). Motorola 68HC11 microcontrollers


The Asynchronous Communication Adapter (#ACOM1 or #ACOM2) is a complete serial communicaton subsystem. In addition to providing full duplex communication, it also provides an 8 MHZ clock source for the processor plus control of the reset line to insure a proper start-up sequence. The TRANSMIT, RECEIVE, CLOCK and RESET pins are buffered for additional drive plus Vpp is provided for programming the internal processor eprom if available. The adapter also provides 5 volts and ground which may power the processor or force the MODE pins to logic 0. Direct connection to a board mounted processor may be accomplished with the optional surface mount probe set.

ACOM1 adapter

The sequence for connecting and communicating with the 68HC11 processor is extremely easy. First the required pins are attached to the processor (stand-alone or in-circuit). The processor is reset in boot strap mode. This may be accomplished as a normal power-up sequence or automatically if attached to the ASYNC adapter RESET pin. The special control program is uploaded from the EPROM+ to the 68HC11 using the DEVICE OPTIONS command. Once the program is uploaded, the system indicates that communication has been established. At this point all EPROM+ functions are available to read or program the 68HC11.

The EPROM+ system allows access to any memory area within the 68HC11 processor. This includes EEPROM, EEPROM and RAM. Note that not all members of the 68HC11 family contain all memory technologies. EXAMPLE: The 68HC811E2 contains 2K of EEPROM, 256 bytes of RAM and no EPROM. To make referencing the desired memory area easier, the EPROM+ software automatically maps the beginning of the selected block to 0. The illustration shows the EEPROM area of a 68HC711E9 which has been selected and mapped to 0. Note that the EEPROM area, which normally exists between B600 and B7FF in the 68HC711E9 memory map, now appears as a single block existing between 0 and 1FF (512 bytes) in the system buffer. The selected memory always appears as a single block beginning at 0 and ending at the last address of the memory area. This makes referencing the memory block fast and easy when simple changes need to be made. The EPROM+ software automatically selects EEPROM memory first and then EPROM if no EEPROM is available.
68HC11 eeprom memory map

You may change the area of access from the default assuming that the processor with which you are working contains an additional memory type. The EPROM+ software allows you to choose between EEPROM, EPROM or the entire 64K address range of the processor. This allows you work directly with a specific memory area as a single block or the entire processor address space. The area of access is changed in an option using the Z command. If you select the entire 64K address space, you will have access to all processor memory areas as they appear in the normal memory map. This is a very powerful feature and is covered in detail in the following section.


The standard access provided for EEPROM/EPROM reading and programming are more than adequate for typical maintenance and service applications. The software, however, has features for the technically advanced user who has interest in product development or testing of existing systems. For these users the following features are provided:

This feature allows you to load any program into the system buffer and upload it into the 68HC11 via bootstrap mode. The upload byte count may be fixed at 256 bytes or established by the user.

This feature allows you to access the entire 64K address space of the processor. This includes all memory plus RAM and I/O. You may directly read and write I/O ports and processor RAM. Use this feature with care as you may also write into the area which contains the EPROM+ control program. In the 64K access mode all memory and I/O exist at their normal addresses within the processor address space.

This feature allows you to select the programming algorithm used by the EPROM+ software while accessing the 64K address space. EXAMPLE: If you wish to program the EEPROM in a 68HC11E9, you must choose the EEPROM algorithm. If you wish to write data to an output port you must choose the MEMORY WRITE algorithm. You therefore have the ability to select the proper algorithm to perform work in the memory area in which you have interest.

This feature is specifically intended for users who are interested in product development, program testing or education. The EPROM+ software allows you to transfer control to a program you have placed into the RAM, EEPROM or EPROM memory of the processor. You may place your program into the 68HC11 by first loading your program into the system buffer and then using the buffer editor "WRITE" command or "PROGRAM" command. Your program may exist at any executable location in the processor memory map. Once your program exists in the 68HC11 memory, a special option allows you to specify that the EPROM+ software transfer control to a physical address within the processor specified by you. This causes your program to execute at the address you specified.

Although you may transfer control to your program, it is many times helpful to have some way for your program to return information to you. The EPROM+ software has a feature whereby your program may place a byte in ACCUMULATOR A and jump to a subroutine (JSR) at a fixed address in the control program. The subroutine at this address will then send the byte back to the EPROM+ system where it is displayed on the screen. This feature allows you to send data back to the EPROM+ from your program thereby allowing you view information or status regarding your programs execution.

If you choose, you may return control to the EPROM+ software from your user program. This is accomplished by performing a JMP to another fixed address within the 68HC11 control program. This will return control to you and again allow direct access to the 64K processor address space.

With the above mentioned software features you are provided with a set of tools which permit direct access to the 68HC11 processors 64K address space. You may write programs and place them into the memory of the processor. You may then execute the program and monitor results via the special EPROM+ software features. After your program execution is complete, you may return control back to the EPROM+. These capabilities combine to form a complete software development package which is more than adequate for fundamental system debug and testing.