19.3.15Single Parameter Data Size Limit

With the Instrument’s system exclusive message format, the size of a single message cannot exceed 256 bytes. The data size and the array size, however, can cause a packet to exceed 256 bytes when transferring a single parameter array. In this case, the IPS and IPR message data length and data index number values can be modified to enable division of a single parameter value into multiple messages so it can be sent that way.

19.3.16img : Parameter Set Image

Format: LSB 0dddddddB

0cccccccB

MSB 000000abB

For a bulk data transfer operation, the parameter set data to be transferred is read sequentially in 16-bit units starting from the top address. Read values are divided into 3-byte segments as shown below, and then sent in sequence.

The following is the conversion format, which is the same as the individual parameter 16-bit transfer detailed above.

16-bit Memory Image

MSB: abccccccB

LSB: cdddddddB

↓

data0: 0dddddddB

data1: 0cccccccB

data2: 000000abB

If the length of the data begin transferred is an odd number of bytes, the final bit field is filled in with zero.

Parameter Set Packet Division The maximum image size of the parameter set that can be sent with one packet is 128 bytes. When data that exceeds 128 bytes is transferred, data is always divided into 128-byte units, except for the final packet. Because of this, the data in received packets can be stored in an areas the size of [P arameterSetStartAddress] + [P acketNumber] × 128.

For bulk parameter set transfer, the 16-bit image is divided in 3-byte groups, so the img field length is the value produced by multiplying the len value (len + 1 when len is an odd number) by 3/2. Note, however, that a parameter set of 128 bytes or less can be sent using a single packet, and anything greater than 128 bytes is divided among multiple packets. This means that the maximum length “data” field is 128 × 3/2 = 192 bytes.

Only one parameter set can be transferred per session, and data from different parameter sets cannot be mixed within a single packet, even when sending multiple parameter sets. Different parameter sets are always divided into separate packets.

19.3.17sum : Check Sum

Format: 0sssssssB

In this case, this “sum” field contains a value, which, when added to the total value of the “img” field, makes the lower seven bits 0. The receiving side checks if this is true, and performs error handling (re-request, etc.) if it is not.

28