The operating procedures consist of assembly-disassembly and downloading descriptions and examples. The EVBU contains a user reset switch S1. This switch is a momentary action pushbutton switch that resets the EVBU and MCU circuits.
Upon reset, the monitor detects the state of the PE0 line (governed by the position of jumper J2). If a low state is detected, the monitor program is executed and the prompt displayed. If a high state is detected, the monitor will automatically jump directly to EEPROM (address location $B600) and execute user program code without displaying the monitor prompt.
As mentioned earlier, user code can be assembled in two ways, one by using the line assembler in the BUFFALO monitor program, and the other by downloading the assembled code from a host computer in Motorolla S-record format. A download to EEPROM will work if the baud rate is slow enough to allow EEPROM programming. Since erasure and programming both require 10 milliseconds, a slow baud rate (300 baud) will have to be used to ensure enough time between characters. If the EEPROM is bulk erased prior to downloading, 600 baud allows enough time between characters.
The Baud rate can be changed by writing an appropriate number into the Baud register in the MCU, and also by using one of the menu options on the communication program (Kermit or Procomm) on the PC. We will discuss about the Baud rates when we come to the communication part of the project.
A standard input routine controls the EVBU operation while the user types a command line. Command processing begins only after the command line has been terminated by depressing the keyboard carriage return key. The command line format is as follows:
> <command> [<parameters>] (RETURN)
where
> EVBU monitor prompt.
<command> Command mnemonic(single letter for most commands).
<parameters> Expression or address.
(RETURN) RETURN keyboard key - depressed to enter command.
The command line format is defined using special characters which have the
following syntactical meanings:
<> Enclose syntactical variable
[] Enclose optional fields
All input numbers are interpreted as hexadecimal. All input commands are converted automatically to upper case lettering except for downloading commands sent to the host computer, or when operating in the transparent mode. A maximum of 35 characters may be entered on a command line. Command line errors can be corrected by backspacing or by aborting the command(CTRL-X or DELETE). Pressing (RETURN) will repeat the most recent command. The LOAD command is an exception. The list of commands with their exact syntax can be looked up from the EVBU User's Manual.