Modem Interrupt Description
MC1321x Reference Manual, Rev. 1.6
8-4
Freescale Semiconductor
attempting any further transceiver active operations (TX, RX or CCA). If the status bit is not cleared, any
subsequent active operation will abort immediately. This condition occurs because the LO1 unlock causes
an operation abort and the status bit must be cleared or any follow-on operation will also abort.
The best practice is to enable the pll_lock_irq interrupt so that IRQ will be asserted if an unlock occurs.
•
If the pll_lock_irq interrupt is not enabled and an LO1 unlock occurs, no rx_rcvd_irq status will be
set for an RX operation nor will a cca_irq status be set for a CCA operation because the operation
was aborted. As a result, an interrupt cannot be generated, and any follow-on operation will be
aborted.
•
If the pll_lock_irq interrupt is not enabled for a TX operation and an unlock occurs, the tx_sent_irq
status will be set when the TX aborts, so an interrupt can be generated. However, any follow-on
operation will still be aborted if the IRQ_Status Register is not read.
8.3
Attn_irq Status Bit and Interrupt Operation
Section 5.28, “IRQ_Status - Register 24”
, attn_irq status bit indicates:
•
The transceiver has achieved Idle status (full power-up) after the release of the RST signal. The
default condition out of reset leaves the attn_irq interrupt request enabled, and upon the transceiver
reaching Idle, the attn_irq status is set and the IRQ signal is asserted
•
Signal ATTN has been asserted (normally to release the transceiver from Hibernate or Doze mode)
and the transceiver has exited the low power mode. The IRQ signal will be asserted if the interrupt
has not been masked
8.4
Interrupts from Exiting Low Power Modes
The modem has three low power modes and interrupt generation differs somewhat for each mode.
8.4.1
Exiting Off Mode (Reset)
The transceiver is put in reset and stays in reset (Off Mode) through the assertion of RST. The initialization
done at reset enables attn_mask which allows an interrupt request when attn_irq is set. One condition that
sets attn_irq is when the transceiver exits reset after RST is released high. As a result, an interrupt request
will always be generated by attn_irq status when reset is exited.
8.4.2
Exiting Hibernate Mode
Hibernate is normally only exited through assertion of ATTN (obviously RST can still override). The
attn_irq status will be set by the assertion of ATTN. If an interrupt is desired to signify the event, the
attn_mask bit must be set before entering Hibernate. The interrupt request will then be generated due to
the attn_irq being set true upon exit from Hibernate.
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