Date: 08-27-88 From: GEORGE HENDERSHOT SYSTEM EXCLUSIVES FOR THE ROLAND MT-32 The documentation that is provided with the Roland MT-32 is unclear to say the least, as it relates to determining the checksum needed for data transfer via system exclusive messages. The checksum needed for the transfer is determined by calculating the sum of the address and each byte of data following the address up to and including the byte just prior to the checksum. It certainly helps to have a calculator that can work with hexadecimal arithmetic. For example, assume that you want to send the following to the MT-32: F0 41 10 16 12 03 02 00 7F 64 07 01 7F 11 F7 F0 indicates the start of the system exclusive 41 is the Roland identification number 10 is the device identification number 16 is the model ID for the MT-32 12 is the Data Set Command (DT1) 03 02 00 is the starting address for the data 7F 64 07 01 7F represents the data you might be sending. 11 is the checksum F7 indicates the end of the system exclusive The checksum of 11 is determined by by adding all the bytes starting at the address until the end of the data. In this example, starting with the 03 in the address and ending with the 7F just to the left of the checksum of 11. This total is 16F. When you have this answer subtract by 100's or 80's until the number is less than 80. In this case subtract 100 from the 16F. Now you have 6F which is less than 80. Since we want the last 7 bits of the number to be zero we are looking for the hex number 80H which is 10000000 binary. Subtract 6F from 80 and the checksum result is 11. (6FH + 11H = 80H)