Modem Modes of Operation
MC1321x Reference Manual, Rev. 1.6
Freescale Semiconductor
7-9
4. tx_sent_mask, Control_A Register 06, Bit 9 is programmed to “1” to enable an interrupt request
when the TX packet has been sent.
5. The MCU loads the value of the number of data bytes plus two (for FCS) into tx_pkt_length[6:0]
TX_Pkt_Ctl Register 03, Bits 6 - 0.
6. The MCU then pre-loads the number of actual data bytes into tx_pkt_ram[15:0] TX_Pkt_RAM
register 02 with a recursive SPI write. An odd number of data bytes requires stuffing a dummy byte
due to the 16-bit SPI data format.
7. Transceiver sequence is programmed to xcvr_seq[1:0] = 0x3 for transmit.
8. RXTXEN must be asserted and held high.
9. When the packet is successfully transmitted, tx_sent_irq reports the completion of packet
transmission, where a “1” indicates a complete status. Also, an interrupt is generated due to the
valid status.
10. In response of the interrupt request from the MC1321x, the microcontroller reads the status to clear
the interrupt and check successful transmission.
7.3.4
Stream Mode Data Transfer TX and RX Operation
Stream Mode does not use the onboard buffer RAMs and presents the data to the SPI buffer on a
word-by-word basis. The Idle Mode is the condition from which RX and TX modes are initiated. In Stream
Mode, control bits tx_strm, rx_strm and use_strm_mode control transition to RX or TX modes
(xcvr_seq[1:0] must equal 00 for Idle). However, the RXTXEN signal must also be high for the transition
to occur and if the Event Timer is enabled, the transition will be synchronized to the TC2_Prime compare
event. Once Receive or Transmit is entered, the MC1321x will transition back to the Idle Mode upon
completion of the selected operation.
The selected mode is controlled by:
1. For Stream Mode, xcvr_seq[1:0] field must be cleared to zero.
2. use_strm_mode, Control_B Register 07, Bit 5 - Set to “1” first to enable Stream Mode.
3. rx_strm, Control_A Register 06, Bit 11, and tx_strm, Control_A Register 06, Bit 12 - These bits
are used to initiate RX or TX operation once Stream Mode is selected.
a) rx_strm is set to 1 to initiate a RX sequence (tx_strm stays at 0).
b) tx_strm is set to 1 to initiate a TX sequence (rx_strm stays at 0).
4. RXTXEN signal - The transition to any other active mode from Idle will not occur unless
RXTXEN is asserted high. This signal may be held high to allow the transitions to occur based on
SPI programming and/or Event Timer activity.
5. tmr_trig_en, Control_A Register 06, Bit 7 - When tmr_trig_en is set to “1”, the transition to the
selected active mode will be based on a tc2_prime[15:0] compare function as described in the
Event Timer section. For Stream Mode, tc2_prime[15:0] takes the place of tmr_cmp2[23:0]
making the compare function based on a 16-bit value as opposed to a 24-bit value. Also,
tc2_prime[15:0] uses the tmr2_irq when the transceiver is in Stream Mode. When tmr_trig_en is
cleared to “0”, the transition to the selected active mode is based only on programming of the
stream control bits. For both cases, RXTXEN must be set high.
Содержание freescale semiconductor MC13211
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