Rainbow Electronics ATA5812 - Manual (Page 48)

48
ATA5811/ATA5812 [Preliminary]
4689B–RKE–04/04
Operation Modes
RX Operation The transceiver is set to RX operation with the bits OPM0 and OPM1 in control
register 1
.
The transceiver is designed to consume less than 1 mA in RX operation while being
sensitive to signals from a corresponding transmitter. This is achieved via the polling cir-
cuit. This circuits enables the signal path periodically for a short time. During this time
the Bit-check logic verifies the presence of a valid transmitter signal. Only if a valid sig-
nal is detected the transceiver remains active and transfers the data to the connected
microcontroller. This transfer take place either via the TX/RX data buffer or via the pin
SDO_TMDO. If there is no valid signal present the transceiver is in sleep mode most of
the time resulting in low current consumption. This condition is called RX polling mode.
A connected microcontroller can be disabled during this time.
All relevant parameters of the polling logic can be configured by the connected micro-
controller. This flexibility enables the user to meet the specifications in terms of current
consumption, system response time, data rate etc.
In RX mode the RF transceiver is enabled permanently and the Bit-check logic verifies
the presence of a valid transmitter signal. If a valid signal is detected the transceiver
transfers the data to the connected microcontroller. This transfer take place either via
the TX/RX data buffer or via the pin SDO_TMDO.
RX Polling Mode If the transceiver is in RX polling mode it stays in a continuous cycle of three different
modes. In sleep mode the RF transceiver is disabled for the time period T
Sleep
while con-
suming low current of I
S
= I
I DL E _ X
. During the start-up period, T
S t a rt u p _P L L
and
T
Startup_Sig_Proc
, all signal processing circuits are enabled and settled. In the following
Bit-check mode, the incoming data stream is analyzed bit by bit contra a valid transmit-
ter signal. If no valid signal is present, the transceiver is set back to sleep mode after the
period T
Bit-check
. This period varies check by check as it is a statistical process. An aver-
age value for T
Bit-check
is given in the electrical characteristics. During T
Startup_PLL
the
current consumption is I
S
= I
RX_X
. During T
Startup_Sig_Proc
and T
Bit-check
the current con-
sumption is I
S
= I
Startup_Sig_Proc_X
. The condition of the transceiver is indicated on pin
RX_ACTIVE (see Figure 40 on page 50 and Figure 41 on page 51). The average cur-
rent consumption in RX polling mode I
P
is different in 1 battery application, 2 battery
application or car application. To calculate I
P
the index X must be replaced by VS1, 2 in
1 battery application, VS2 in 2 battery application or VS2, VAUX in car application (see
section “Electrical Characteristics”)
Table 37. Control Register 1
OPM1 OPM0 Function
1 0 RX polling mode
1 1 RX mode
I
P
I
IDLE_X
T
Sleep
I
Startup_PLL_X
T
×
Startup_PLL
I
RX_X
T
Startup_Sig_Proc
T
Bitcheck
+
( ) Ч
+ +
Ч
T
Sleep
T
Startup_PLL
T
Startup_Sig_Proc
T
Bit_check
+ + +
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- =