Maxim Integrated 71M6521BE Energy Meter IC Family Software - Manual (Page 55)

71M652X Software User’s Guide
Revision 1.7 TERIDIAN Proprietary 55 of 138
© Copyright 2005-2007 TERIDIAN Semiconductor Corporation
RTC interrupt happens, and then the XFER interrupt happens after the IE_XFER flag is already tested, but before the
RTC interrupt is cleared. In this case, the signal to EXT6 will remain set, and never have an edge to cause another
interrupt 6. Therefore, the XFER_BUSY interrupt will hang forever, thus preventing delivery of the data to the meter.
To prevent this error condition, at the end of the XFER_BUSY_RTC service routine, both interrupt flags are again
checked, and when at least one of them is active, the processing starts again.
Both interrupts have a backup check - the main watchdog timer is never reset unless both interrupts run.
5.4.2.1 SERIAL Interrupt
es0_isr is the ISR servicing UART 0. In this ISR, the UART data is sent and received along using flow control, if
enabled. Parity and other serial controls are managed in this ISR. The alternative serial port, UART 1 uses an ISR with
identical code structure (es1_isr).
es0_isr()
RX interrupt
RI == TRUE?
Call high-level protocol to
receive byte
no
yes
END
TI == TRUE?
TX interrupt
yes
Call high-level protocol to
transmit byte
no
es1_isr()
RX interrupt
RI == TRUE?
Call high-level protocol to
receive byte
no
yes
END
TI == TRUE?
TX interrupt
yes
Call high-level protocol to
transmit byte
no
Figure 5-10: Serial 0 and 1 isr