Rainbow Electronics ATA5812 - Manual (Page 58)

58
ATA5811/ATA5812 [Preliminary]
4689B–RKE–04/04
TX Operation The transceiver is set to TX operation by using the bits OPM0 and OPM1 in the control
register 1.
Before activating TX mode, the TX parameters (baud rate, modulation scheme ... ) must
be selected as illustrated in Figure 50 on page 59. The baud rate depends on Baud 0
and Baud 1 in control register 6, Lim_min0 to Lim_min5 in control register 5 and XLIM in
control register 4 (see section “Control Register”). The modulation is selected with
ASK_/NFSK in control register 4. The FSK frequency deviation is fixed to about
± 16 kHz. If P_Mode is set to 1, the Manchester modulator is disabled and pattern mode
is active (NRZ, see Table 41 on page 61).
After the transceiver is set to TX mode the start-up mode is active and the PLL is
enabled. If the PLL is locked, the TX mode is active.
If the transceiver is in start-up or TX mode, the TX/RX data buffer can be loaded via the
4-wire serial interface. After the first byte is in the buffer and the TX mode is active, the
transceiver starts transmitting automatically (beginning with the MSB). While transmit-
ting it is permanently possible to load new data in the TX/RX data buffer. To prevent a
buffer overflow or interruptions during transmitting the user must ensure that data is
loaded at the same speed as it is transmitted.
There is a counter that indicates the number of bytes to be transmitted (see section
“Transceiver Configuration”). If a byte is loaded, the counter is incremented, if a byte is
transmitted, the counter is decremented. The counter value is available via the 4-wire
serial interface. An IRQ is issued, if the counter while counting backwards reaches the
value defined by the control bits IR0 and IR1 in control register 1.
Note: Writing to the control register 1, 4, 5 or 6 during TX mode, resets the TX/RX data buffer
and the counter which indicates the number of bytes to be transmitted.
If T_Mode in control register 1 is set to 1, the transceiver is in TX transparent mode. In
this mode the TX/RX data buffer is disabled and the TX data stream must be applied on
pin SDI_TMDI. Figure 50 on page 59 illustrates the flow chart of the TX transparent
mode.
Table 40. Control Register 1
OPM1 OPM0 Function
0 1 TX mode