!lm12
!rm75
More About the EPSON Interface................Peter Bartlett

Whoops!  I left out something in my instructions for modifying the EPSON interface card!

The software driver on the interface card is $100 bytes long, and resides in the first 256 bytes of the 1024-byte EPROM.  However, the folks at EPSON got a couple of the address lines mixed up.  Burning a new EPROM is not as straightforward as it should be.

The problem is that chunks of the program are shuffled.  To understand, consider the $100 bytes to be divided into 4 parts of $40 bytes each.  Part 0 is $0 to $3F, part 1 is $40 to $7F, part 2 is $80 to $BF, and part 3 is $C0 to $FF.  When blasting the EPROM, the sequence of these parts must be changed.  Instead of 0,1,2,3, the sequence must be 1,0,3,2.

When you list the contents of the EPROM while it is in the EPSON card, the contents appear normal.  But if you remove the EPROM from the card and read it with another device, it will be in its juggled format.

Another point worth emphasizing is that this fix does not allow characters with the high-bit set to pass through the normal software driver.  This driver is only compatible with the Apple's normal ASCII output.  However, both Applesoft and machine language programmers can send 8-bit characters by bypassing the card as described last month in my article.
