Cypress CY4672 manual Byte Name, 0xFC, Modifier Reserved Scan Code Keys 0x00 0x04

Keyboard

done to optimize the packet size based on the fact that the most common report has only one non- zero scan code without a modifier. The full Standard 101 Keys report format is shown in Table 4-5.

Table 4-5. Standard 101 Keys Report Format

Byte	Name
2	Scan Code 1
	(< 0xFC)

3Modifier Keys

4Scan Code 2

5Scan Code 3

6Scan Code 4

7Scan Code 5

8Scan Code 6

Example

The following reports is sent if a user presses an ‘a’ on the keyboard. The down key packet sent from the keyboard to the bridge is shown in Table 4-6.

Table 4-6. Example ‘a’ Down Key Standard 101 Keys Report

Byte 2

Scan Code 1

0x04

The bridge then adds the trailing zeros, inserts the reserved byte, rearranges the modifier and scans code 1 bytes and removes the packet header to produce the USB report shown in Table 4-7.

Table 4-7. Example USB Report for the ‘a’ Down Key

Modifier	Reserved	Scan Code	Scan Code	Scan Code	Scan Code	Scan Code	Scan Code
Keys		1	2	3	4	5	6
0x00	0x00	0x04	0x00	0x00	0x00	0x00	0x00

The up key packet sent from the keyboard to the bridge (all data bytes are zero) is shown in Table 4-8.

Table 4-8. Example Up Key Standard 101 Keys Report

Byte 2

Scan Code 1

0x00

The bridge then adds the trailing zeros, inserts the reserved byte, and removes the packet header to produce the USB report shown in Table 4-9.

Table 4-9. Example USB Report for a Standard 101 Key Null Packet Report

Modifier	Reserved	Scan Code	Scan Code	Scan Code	Scan Code	Scan Code	Scan Code
Keys		1	2	3	4	5	6
0x00	0x00	0x00	0x00	0x00	0x00	0x00	0x00

CY4672 Reference Design Guide, Document # 001-16968 Revision ** 67

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