Datasheet

Functional description ST7540
34/44
Function Value Selection Note Default
Bit 13 Bit 12
12 to 13
Detection
method
Preamble detection
without conditioning
00
Preamble detection
notification on CD_PD Line
CLR/T and RxD signal always
present In UART Mode
(UART/SPI pin set to 1) this
configuration is not allowed.
Carrier
detection
without
conditioning
Preamble detection
with conditioning
01
Preamble Detection
notification on CD_PD Line.
CLR/T and RxD line are
forced to "0" when Preamble
has not been detected or PLL
is in Unlock condition. In
UART Mode (UART/SPI pin
set to 1) this configuration is
not allowed.
Carrier detection
without conditioning
10
Carrier detection notification
on CD_PD Line
CLR/T and RxD signal always
present
Carrier detection
with conditioning
11
Carrier detection notification
on CD_PD Line
CLR/T Line is forced to “0”
and RxD Line is forced to “0”
or “1” (according the
UART/SPI pin level) when
carrier is not detected
Bit 14
14
Mains
Interfacing
Mode
Synchronous
Asynchronous
0
1
Asynchronous
Bit 16 Bit 15
15 to 16 Output Clock
16 MHz
8 MHz
4 MHz
Clock OFF
0
0
1
1
0
1
0
1
4 MHz
Bit 17
Active only if extended control
register is enable (Bit 21=”1”)
17
Output
Voltage Level
Freeze
Enabled
Disabled
0
1
Disabled
Bit 18
Active only if extended control
register is enable (Bit 21=”1”)
18
Header
Recognition
Disabled
Enabled
0
1
Disabled
Bit 19 Active only if header
recognition function (Bit
18=”1”) and extended control
register (Bit 21=”1”)
are enable
19
Frame Length
Count
Disabled
Enabled
0
1
Disabled
Table 12. Control register functions