Datasheet

ST7540 Functional description
35/44
Function Value Selection Note Default
Bit 20
Active only if Extended
Control Register is enable (Bit
21=”1”)
20
Header
Length
8 bits
16 bits
0
1
16 bits
Bit 21
Extended Register enables
Functions on Bit 17, 18,19 and
20
21
Extended
Register
Disable (24 bits)
Enabled (48 bits)
0
1
Disabled
(24 bits)
Bit 22
22
Sensitivity
Mode
Normal Sensitivity
High Sensitivity
0
1
Normal
Bit 23
23 Input Filter
Disabled
Enabled
0
1
Disabled
24 to 39
Frame
Header
from 0000h to
FFFFh
One 16 bits Header or two 8
bits Headers (MSB first)
depending on Bit 20
9B58h
40 to 47 Frame Length from 01h to FFh
Number of 16 bits words
expected
08h
Table 12. Control register functions