The protocol used for getting a screenshot is shown below. For information on packet formats, click here.

Step	Direction			Packet
1				SCR
2				ACK
3				DATA - Format described below.
4				ACK

The data packet contains a 3840-byte monochrome bitmap (1 bit per pixel). Each bit has a value of 1 if the corresponding pixel is dark or a value of 0 if the corresponding pixel is light.

The pixel order is left-to-right, then top-to-bottom (See figure below).
Byte 0 defines the first 8 pixels in the left side of the top row of the screen. Bytes 1-29 define the rest of the first row, bytes 30-59 define the second row, etc.

Example:

PC:	08 6D 00 00	Screenshot request
TI:	98 56 00 00	Acknowledgement of request
	98 15 00 0F <3840 bytes plus 2 byte checksum>	Screen data
PC:	08 56 00 00	Acknowledgement of data

The following figure demonstrates byte ordering of the pixels if the bitmap is in a 3840-element array data[]:

Remark: contrary to the TI92/92+ calculator, only the 160x100 upper rectangle is visible on the TI89. The remaining bytes are usable (in assembler for instance) but they are not visible. So, a clipping is necessary once the screenshot have been got.

Note that this format is different from the standard Windows bitmap format, which specifies a value of 1 if the pixel is light and bottom-to-top row order.
 

Packet Formats

Table of Contents

Manual Transfers