Because silent linking protocols are one-sided (i.e. the user interaction is solely on the computer), there are three different transfer sequences required. First a directory listing must be downloaded from the calculator in order to choose the variables to transfer or to check for duplicate names and out-of-memory conditions. Then, if variables are to be downloaded, a variable request action must be initiated by the computer. Finally, if variables are to be uploaded, a request-to-send action must be sent by the computer.

Directory Listing

The protocol for requesting a directory listing is shown below. For information on packet formats, click here.

Step	Direction			Packet
1				REQ with data type=19h (see note under Type ID's for variable header format) and with a particular filter.
2				ACK
3				VAR - a variable information packet (see format below)
4				ACK
5				CTS
6				ACK
7				DATA - a variable entry (see format below).
8				ACK
9				CONT or EOT - if CONT, then go to step 4.
10				ACK

The request has the following format according to the operation (global directory list or local directory list):

Offset	Length	Description
0	4 bytes	Always {00h, 00h, 00h, 00}.
4	1 bytes	This byte always has a value of 19h (directory list request).
5	1 byte	The length, in characters, of the name field. Here, it is always 0.

The data in the variable information packet has the following format:

Offset	Length	Description
0	4 bytes	Unknown.
4	1 bytes	This byte always has a value of 53h (???).
5	1 byte	The length, in characters, of the name field. Always 04h.
6	4 bytes	The name of the current folder. Always "main".

The var section (data packet) of the transfer is always 18 bytes long and takes the following format:

Offset	Length	Description
0	4 bytes	These four bytes always have a value of 0.
4	8 bytes	Variable name padded with NULL chars if necessary.
12	1 byte	Variable type ID.
13	1 byte	Variable attribute: 00h = unlocked, 01h = locked.
14	4 bytes	If folders are listed, this field contains the number of variables in this folder. If variables are listed, this field contains the length, in bytes, of the variable data for this variable without the extra four bytes at the beginning of the data packet.

Example: (to do, my examples are too big !)
 

PC:	09 A2 06 00 00 00 00 00 19 00 39 00	Directory list request
TI:	89 56 00 00	Acknowledgement of request
	89 06 0A 00 0E 00 00 00 5304 6D 61 69 6E 03 52 02	Variable header - complete directory starting with "main".
PC:	09 56 00 00	Acknowledgement of header
	09 09 FF FF	Clear to send
TI:	89 56 00 00	Acknowledgement of clear to send
	89 15 12 00 00 00 00 00 41 00 00 00 00 00 00 00 03 00 01 00 00 00 66 13	Variable entry - Unlocked folder "base" with one variable
PC:	09 56 00 00	Acknowledgement of variable entry
TI:	89 78 00 00	Continue
PC:	09 56 00 00	Acknowledgement of header
	09 09 FF FF	Clear to send
TI:	89 56 00 00	Acknowledgement of clear to send
	89 15 12 00 00 00 00 00 42 00 00 00 00 00 00 00 03 00 01 00 00 00 66 13	Variable entry - Unlocked folder "base" with one variable
PC:	09 56 00 00	Acknowledgement of variable entry
TI:	89 92 00 00	End of transmission - no more variables
PC:	09 56 00 00	Acknowledgement of EOT

Requesting a Variable

Step	Direction			Packet
1				REQ with expected header including the folder name, if necessary
2				ACK (see note below)
3				VAR (specifing the size without the extra four bytes) with actual header and no folder name
4				ACK
5				CTS
6				ACK
7				DATA with an extra four bytes at the beginning of the packet
8				ACK
9				EOT
10				ACK

As with manual transfers, the data section contains the variable data. For information on variable formats, click here.

Example:

PC:	09 A2 0C 00 00 00 00 00 00 06 6D 61 69 6E 5C 64 93 02	Request Known Variable  "d" in the "main" folder
TI:	89 56 00 00	Acknowledgement of request
	89 06 08 00 05 00 00 00 00 01 64 6A 00	Variable Header: String "d"
PC:	09 56 00 00	Acknowledgement of variable header
	09 09 FF FF	Clear to send variable
TI:	89 56 00 00	Acknowledgement of CTS
	89 15 09 00 00 00 00 00 00 03 01 01 1F 24 00	Variable data: ?
PC:	09 56 00 00	Acknowledgement of variable data
TI:	89 92 00 00	End Of Transmission
PC:	09 56 00 00	Acknowledgement of EOT

Sending a Variable

The protocol for sending a variable to the calculator is shown below.

Step	Direction			Packet
1				RTS (specifing the size with the extra four bytes)
2				ACK
3				CTS or SKIP/EXIT (see note below)
4				ACK
5				DATA
6				ACK
7				EOT - if there are several variables to transmit, steps 7 and 8 can be skipped until the last variable.
8				ACK

Note: If the calculator sends a MEM packet in step 3, it does not have enough free memory to accomodate the variable. In this case, step 3 will be the end of the transfer.

Again, the data section contains the variable data.

Example:

PC:	09 06 0D 00 0C 00 00 00 0C 07 74 64 73 5C 73 74 72 20 03	Request to send String "str" in the "tds" folder
TI:	89 56 00 00	Acknowledgement of request
	89 09 00 00	Clear to send variable
PC:	09 56 00 00	Acknowledgement of CTS
	09 15 0C 00 00 00 00 00 00 06 00 61 62 63 00 2D 59 01	Variable data: "abc"
TI:	89 56 00 00	Acknowledgement of data
PC:	09 92 00 00	End Of Transmission
TI:	89 56 00 00	Acknowledgement of EOT

Manual Transfers

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