MagTek MICRSafe99875466 - Manual (Page 45)

Section 5. USB Communications
37
GET KEYMAP ITEM COMMAND
Command number:
3
Description: This command is used to get a key map item from the active key map.
The active key map is determined by the active key map property. Data
from a card or check is a sequence of ASCII characters. These ASCII
characters are mapped to key strokes and these key strokes are sent to the
host to represent the ASCII character. The key map maps a single ASCII
character to a single USB key usage ID and USB key modifier byte. The
key usage ID and the key modifier byte are transmitted to the host via USB
to represent the ASCII character. The ASCII value is the value of the
ASCII character to be transmitted to the host. See the ASCII table in
Appendix D for the values of the ASCII character set. The USB key usage
ID is a unique value assigned to every keyboard key. For a list of all key
usage IDs see Appendix E. The key modifier byte modifies the meaning
of the key usage ID. The modifier byte indicates if any combination of the
right or left Ctrl, Shift, Alt or GUI keys are pressed at the same time as the
key usage ID. For a list and description of the key modifier byte see
Appendix F.
When both the key usage ID and the key modifier byte are set to 0xFF for
a given ASCII value, the ALT ASCII code is sent instead of the key map
values. The ALT ASCII code is a key press combination consisting of the
decimal value of the ASCII character combined with the ALT key
modifier. For example, to transmit the ASCII character ‘?’ (063 decimal),
keypad ‘0’ is sent combined with left ALT key modifier, next keypad ‘6’
is sent combined with the left ALT key modifier, last keypad ‘3’ is sent
combined with the left ALT key modifier.
Data structure:
Request Data:
Offset Field Name Description
0 ASCII value Value of the ASCII character to be
retrieved from the key map. This can be
any value between 0 and 127 (0x7F). For
example, to retrieve the key map item for
ASCII character ‘?’ (card data end sentinel)
use the ASCII value of ‘?’ which is 63
(0x3F).