This application note provides information on how to operate the M68HC11EVB Evaluation Board (EVB) in the special test mode. The EVB is designed to operate the resident MC68HC11xx MCU in the expanded multiplexed mode of operation. A variation of the expanded multiplexed mode is the special test mode, which allows the user special privileges (i.e., no time-out on protected registers, CONFIG register programming, etc.). The special test mode can be used if, for some reason, the configuration (CONFIG) register gets corrupted and the user needs to change the register contents.
ENTERING THE SPECIAL TEST MODE
Entering the special test mode is accomplished by grounding the EVB resident MC68HC11xx MCU MODB pin (jumper connector P1 pins 1 and 2) and initiate a reset condition by pressing the RESET switch S1. The special test reset vector resides at locations $BFFE and $BFFF versus $FFFE and $FFFF for normal modes of operation. The RAM/EPROM socket (U4) is remapped by removing the jumper on jumper header J3 and reinstalling the jumper on jumper header J7. Socket U4 is now remapped from $A000 through $BFFF for user application program.
CONFIGURATION REGISTER
The configuration (CONFIG) register is an EEPROM byte located initially at $103F in the MC68HC11xx MCU memory map. Upon a reset condition the CPU loads the CONFIG register contents into a set of MCU latches. These latches contain the data which is displayed on the terminal when performing a memory display (MD) operation of the CONFIG register ($103F).
Special test mode operations are described as follows:
a. Enabling COP Watchdog System via CONFIG Register NOCOP Bit
b. MC68HC811A2 Resident MCU Operation
c. Programming an MC68HC811A2 for Single-Chip Applications
d. Clearing CONFIG Register ROMON Bit
Enabling COP Watchdog System via CONFIG Register NOCOP Bit
Suppose the user is finished with initial debugging and wants to enable the computer operating properly (COP) watchdog system by programming the NOCOP bit in the CONFIG register to a logic zero. For MC68HC11xx mask sets B96D and higher, this operation can only be accomplished using either the special test or bootstrap mode of operation.
Steps required:
a. Install 6264 RAM (8Kx8) or equivalent device in socket location U4.
b. Memory modify (MM) locations $BFFE and $BFFF to contain $E00A.
($E00A enables reset vector to jump to BUFFALO.)
c. Remove jumper J3 and reinstall on J7.
d. Jumper connector P1 pins 1 and 2.
e. Press RESET switch S1.
At this point the user should be in the BUFFALO monitor program and operating in the special test mode. By entering MD 103F on the terminal keyboard, the user can display the contents of the CONFIG register latches. For example, if the ROMON bit is a logic zero and the EEON bit is a logic one for an MC68HC11A1 MCU device, the terminal will display $0D.
To turn on the COP, the user enters MM 103F and changes the memory contents to $09. BUFFALO treats EEPROM as a RAM location. The MM command programs the location if found to be EEPROM. If a memory display (MD) of location $103F was again performed, a $0D would be displayed since the CONFIG register latches are not updated until the next reset operation.
MC68HC811A2 Resident MCU Operation
Many users want to operate the MC68HC811A2 device in the EVB as the resident MCU. Using the MC68HC811A2 device will normally cause EVB problems because the erased CONFIG register places the 2K of EEPROM at locations $F800-FFFF. Locations $F800-FFFF will be in conflict with the BUFFALO monitor program in EPROM. However, by operating in the special test mode, the CONFIG register EEON bit is forced to a logic zero. At this point, the user must move the EEPROM to a location other than $E800-EFFF or $F800-FFFF and then turn the EEPROM back on.
Steps required:
a. Install 2764 EPROM (8Kx8) or equivalent device in socket location U4 with
EPROM locations $1FFE and $1FFF programmed to contain $E00A.
($E00A enables reset vector to jump to BUFFALO.)
b. Remove jumper J3 and reinstall on J7.
c. Jumper connector P1 pins 1 and 2.
d. Press RESET switch S1.
At this point the user should be in the BUFFALO monitor program and operating in the special test mode. By entering MD 103F on the terminal keyboard, the user can display the contents of the CONFIG register latches. For example, if the MCU device was previously erased, the CONFIG register latches would contain $FE (not $FF since in EEON bit is initially forced to a logic zero). To move the EEPROM to another location, the user enters MM 103F and changes the CONFIG register latch contents to $xF (where x is the high-order byte of the address desired; again x cannot be $E or $F).
NOTE
When using the MC68HC811A2 device, the user writes directly to the CONFIG register latches; therefore, memory display (MD) of $103F will result in the changed value to be displayed without resetting the MCU.
Programming an MC68HC811A2 for Single-Chip Applications
If the user requires a target system MC68HC811A2 device to operate in a single chip mode, the user must have 2K of EEPROM turned-on via the CONFIG register EEON bit , and the 2k of EEPROM must be remapped to $F800-FFFF. To accomplish this on the EVB, the user must first move the 2K EEPROM to another location other than $E800-EFFF or $F800-FFFF and then turn the EEPROM back on. The user must then inform the BUFFALO monitor program that the EEPROM does not reside at the starting location $B600 via the modify EEPROM range (EEMOD) command. (The reassigned starting location will also indicate that the device is not an MC68HC11A1 MCU.)
Another problem exists in that the EVB RAM is located at $C000 through $DFFF, and a user program originated at $F800 through $FFFF cannot be downloaded into the EVB RAM. This problem is now corrected via the addition of the OFFSET command. The OFFSET command will either add or subtract a hexadecimal value from the S-record address locations.
The EEMOD and OFFSET commands were added to the BUFFALO monitor program (Rev 3.4). Rev 3.4 of the BUFFALO monitor program is available on the Motorola's freeware line, (512)-440-FREE.
As shown on the following page, the user programs the 2K of EEPROM via the MOVE command, and then reprograms the CONFIG register to place the EEPROM back to locations $F800-FFFF. The example also assumes that a 2K program was downloaded into socket location U5 (at location $C800). This can be accomplished by downloading a user program originally originated at $F800 through $FFFF as follows:
Enter:
>OFFSET -3000 Subtract 3000 from S-record address.
D000 Positive offset added to S-record address.
>
>LOAD cat filename.S19 Address locations $F800-FFFF become
$C800-CFFF.
DONE
>
Programming an MC68HC811A2 for Single-Chip Applications (cont'd)
Steps required:
a. Install 2764 EPROM (8Kx8) or equivalent device in socket location U4 with
locations $1FFE and $1FFF programmed to contain $E00A.
($E00A enables reset vector to jump to BUFFALO.)
b. Remove jumper J3 and reinstall on J7.
c. Jumper connector P1 pins 1 and 2.
d. Press RESET switch S1.
e. Enter:
>MM 103F Examine location $103F.
103F FE 8F(RETURN) Move EEPROM to $8800-8FFF.
>
>EEMOD 8800 Inform BUFFALO of EEPROM location.
>
>MOVE C800 CFFF 8800 Program 2K EEPROM (approx. 30 sec.)
>
>MM 103F Examine location $103F.
103F 8F FF(RETURN) Move EEPROM back to $F800-FFFF.
> Terminate MM operation.
At this point, power down the EVB, remove the MC68HC811A2 device and reinstall
in target system. BUFFALO will not operate at this time.
Clearing CONFIG Register ROMON Bit
If the CONFIG register ROMON bit in the MC68HC11 MCU device is accidently turned on, the EVB will not operate because ROM is residing at locations $E000-FFFF. BUFFALO also resides at locations $E000-FFFF. In this example, simply activating the special test mode and vectoring to BUFFALO will not work. Therefore the user must not only replace RAM with EPROM, but must also write a small routine that will turn off the CONFIG register ROMON bit.
Steps required:
a. Program 2764 EPROM (8Kx8) or equivalent device with the program supplied
on the following page of this application note.
b. Install programmed 2764 EPROM (8Kx8) or equivalent device in socket
location U4.
c. Remove jumper J3 and reinstall on J7.
d. Jumper connector P1 pins 1 and 2.
e. Press RESET switch S1.
f. Remove jumper previously installed on connector P1 pins 1 and 2.
