Rainbow Electronics AT76C551 - Manual (Page 39)

39
AT76C551
1612D–08/01
• Bit 1 – TxEnable
Set by firmware to start a RX cycle at then next event generated by compare timer
CmpTimer_RxTxStart.
• Bit 0 – RxTx_, Abort
Set by firmware to immediately abort current RX or TX cycle, or to cancel the programmed RX
or TX cycle due to start.
Note: Default Value: 00000000 hex
Provided that bit 1 of TcCtrlStatus register is set the Bluetooth baseband processor has the
ability to automatically generate the sequence of signals necessary to implement TX and RX.
To initiate an automatic RX cycle, the firmware has to program CmpTimer_RxTxStart register
and then set bit 2 of TcCommand register. When the compare timer generates its event the
RX cycle begins and PU_RX/TX signal is raised. After PU_RX/TX settle time the RX_ON sig-
nal is raised. After RX_ON settle time baseband data acquisition circuits are enabled and the
correlator begins to search for a known access code. If correlator is triggered, then the correla-
tor is powered down and RX packet data is acquired. After RX packet completion the RX cycle
ends and the transceiver is powered down.
Note: The transceiver and the correlator will be held active until correlator trigger occurs, or RX cycle
is aborted by firmware, i.e. firmware sets bit 0 of TcCommand register.
To initiate an automatic TX cycle the firmware has to program CmpTimer_RxTxStart register
and then set bit 1 of the TcCommand register. When the compare timer generates its event,
the TX cycle begins and PU_RX/TX signal is raised. After PU_RX/TX settle time the TX_ON
signal is raised causing TX ramp rise. While TX ramp rises, the transmitter is fed with a 0/1-
alternating data stream. After TX_ON settle time (which should include TX ramp set time), the
actual TX packet data stream is given to the transceiver. After TX packet completion, the TX
cycle ends and the transceiver is powered down.
A RX or TX automatic cycle can be aborted at any moment. To abort a current RX or TX cycle
the firmware will set bit 0 of TcCommand register. This will power down the transceiver and
reset all baseband internal state machines to an idle state. To cancel the program, which has
not yet started, RX or TX automatic cycle firmware can also use bit 0 of TcCommand register.
Note: Please note that the baseband is aware of RX or TX packet type and length therefore it has the
ability to trace RX or TX packet fields and decide the FEC encoding, CRC calculation, etc.
TcProg
addr: 600050 hex R/W 32 bits
• Bits 31..26 – Reserved
• Bit 25 – 3wb_, EnableBusy
Set by firmware to initiate serial data send on the 3-wire bus. Reset by hardware to indicate
that 3-wire bus access is complete.
• Bit 2 – 3wb_,ClockRate
0: 3-wire bus clock is generated by system clock division by 4.
1: 3-wire bus clock is generated by system clock division by 8.