Part 2: Retain Buffers & Macros

I agree with the FORUM (3/1) about the disadvantages of the 2050. A user programmable RS-232 interface driving a separate modem is the most versatile combination. I use a Memotech RS232 I/F on my expanded ZX-81 system and have used it to transfer code to a commercial EPROM burner, for example, as well as driving a TRS-80 modem.

However, the price of the 2050 is dropping and the MTERM software has some interesting frills which make it attractive to someone who wants only to make 300 Baud dial-ups.

I was disappointed in having to load auto-dialer and macro settings every time I wanted to use them. The extra time and trouble of loading nullified any benefit. HOT Z AROS and some head scratching showed an initialization routine at the start of the MTERM code which created and cleared the auto-dialer and macro settings during a cold start.

To change MTERM to load auto-dial settings and macros along with the program is easy. Load the program as usual. Set the paper, ink, and border colors to your tastes. Set the system parameters to match the protocol of your favorite dial-up service, and load or key in your auto-dial directory and macro information.

Exit to BASIC from the main menu and POKE 0’s manually, or with a for-next loop in BASIC, into the RAM addresses from 54066 to 54088, (D332 to D348 Hex) inclusive.

SAVE”mterm”CODE 54016,9216 a few times on a fresh tape and VERIFY. You now have an MTERM which will allow you enter from BASIC at the original address of 54016 (D300 Hex) without destroying any of your directory and macros! The extra length of the SAVE is, of course, the tables which were created in RAM by the original cold start routine and which must now be included on the tape.

The next step, if you so desire, is to put the new version on a dock cartridge. I didn’t want to spend the effort to rewrite MTERM to run the code in EPROM and have the tables and variables in RAM. I also didn’t want to interfere with the data buffer feature of MTERM.

The answer is having all the code in EPROM in a cartridge, copying it to RAM and then jumping to the start of the code. The next six bytes added to the code in the area cleared earlier tell the 2068 operating system to ignore the cartridge and allow full use of the MTERM buffer.

POKE 54066,151      Sub A
POKE 54067,211      Out (F4),A
POKE 54068,244
POKE 54069,50       Ld (5CC6),A
POKE 54070,198
POKE 54071,92

SAVE this latest version a few times!

The new version with auto-dial and macro tables included is over 8K bytes, so I chose a 27128 EPROM. I hope you have the JLO 2068 EPROM burner driven from HOT Z AROS. If you are driving the JLO programmer from BASIC, observe the precautions for burning 27128s! The modified version of MTERM from 54016 to 63231 (D300 to F6FF Hex) is burned into the 27128 from 7168 to 16383 (1C00 to 3FFF Hex).

The following is the AROS overhead and the code to copy MTERM into RAM and jump to it. Write or POKE it into a safe area of RAM, 32768+ (8000+ Hex), for instance, then burn it into the EPROM at 0 to 37 (0 to 25 Hex).

Install the EPROM in the cartridge mapped at 32768 (8000 Hex). With the cart installed in the dock, the 2068 should come up at power on with the MTERM title page. You will find all your settings, parameters, dial-up info. and macros intact. Exit to basic from the main menu and you should discover an empty BASIC programming area. Re-enter MTERM with RAND USR 54016 to restart the RAM resident code. This allows you to change settings during a session, exit to BASIC to manipulate the data in the buffer area, or whatever; and restart MTERM with the new settings preserved. A NEW from BASIC will cold start the cartridge and re-establish the settings programmed into the EPROM.

EPROM Addr:   Decimal Value:
     0             1
     1             2
     2             8
     3           128
     4           207
     5             1
     6             0
     7             0
     8             0
     9             0
    10            11
    11             0
    12           249
    13           192
    14           176
    15            34
    16            51
    17            50
    18            55
    19            57
    20            50
    21            34
    22            13
    23           128
    24            33
    25             0
    26           156
    27            17
    28             0
    29           211
    30             1
    31             0
    32            36
    33           237
    34           176
    35           195
    36             0
    37           211