Roland TD-7 - Page 163

>t= The size of the requested data does not ifltiitfitlt? the numher oi hytes
that will mat-te an a l}'i‘t message, hut represents the address fields
where the requested data resides.
=4“ Some models are subject tn limitations in data format used for a
single transaction. Requested data. lnr example, may have a limit
in tength or must he divittett into predetermined address fields before
it is exchanged across the interface.
at The same number of bytes comprises address and size data, which.
ht]W0\'l?F.,\'ll1'_\_' with the .\-lode!-it).
=t= The error checking process uses a checksurn that provides a hit
pattern where the least significant T hits are zero when values for
an address. size. and that checltsum are summed.
=Data set 1 : DT1 t12H.l
This message correstmnrls to the actual data transfer process.
Because every byte in the data is assigned a unique address. a DTI
message can cenve_v the starting address of one or more data as welt
as a series of data formatted in an artdress- dependent order.
The .‘\-tit)! stanttarrts inhibit non-real time messages from interrupting an
e.‘<t:tttsi\'t: one. This tact is intzonvenient for the devices that 5L1{.lptJ|'t a
"sn{lthrnugh" tnechanisrn. To maintain cnmrlatibility with such devices.
Roland has litnited the {I'll to 25t".i hytes sh that an excessively long
message is sent out in separate segments.
*7___. ___ ________ _ i :7. __ ____ _ _____ _ __ _ __
1 Byte Descnotion
1 ‘NH
121-1
in
.61
I
¢-¢-
Q.
....ct_
I
FOH Exclusive
l DEV Device ID
3 MDL Mtildel ti}
Manufacturer FD (Roland)
Command iD
Address MSB A
' 1
Iv-
LS5
i Data
-¢-
4-
‘ sum Check sum
F7H End of exclusive it
___ __ J
=t= A tl'I't message is capable of providing ontit-' the valid data among
those specifier! by an RQI message.
* Some models are subject te limitations in data lermat used for a
sinnle transaction. Requested data. for example. may have a limit
in length or must be divided into predetermined address fields before
it is etttzhanged across the interface.
* The number of bytes comprising address data varies from one Model-
it) to another. '
* The error checking nrtttiess uses a checltsum that provides a bit
pattern where the least significant T hits are zero when values for
an arltiress. size. and that checksum are summed.
=.~Exan1ple of Message Transactions
Oiltevice A sending data to Device ti
Transfer of a t)'t‘t rnessa;-ze is all that takes place.
{Data set 1] ——------~—-—--~—-———-P-
=t= More than 20m set: time internal.
{Data set t] ----—--—-----------------DP
annoy.»
{Data set t]
Roland Exclusive Messages
IDe\-ice ll requesting data from Device A
Device B sends an RQI message to Device A. Checking the
message. Device .-’t sends a DTI message back to Device El.
0...... (B)
[Data set 1] Requeat data]
[Data set 1] -Z------------------P*
=t=More than 20m sec time internal.
[Data set 1] ----------------—--~I-
{Data set t] ------------—-—-----9’