Maxim Integrated High-Speed Microcontroller - Manual (Page 173)

High-Speed Microcontroller User’s Guide
Rev: 062210 173 of 176
17.5 Serial Port Does Not Work
The serial port is not a complicated peripheral, but there are many elements that need to be initialized.
The following checklist is provided to help in debugging.
1) Have the appropriate port latch bits (P3.0, P3.1, P1.2, or P1.3) been set to 1 to enable the serial port
functions?
2) Has the correct time base been selected? (4 clocks per tick or 12 clocks per tick)
3) Is the appropriate timer-reload value loaded?
4) Is the appropriate timer mode selected?
5) Is the appropriate timer running by setting TR0, TR1, or TR2 bits?
6) Is the correct serial port mode selected?
7) If desired, is the serial port doubler bit, SMOD, set? (
PCON .7 or WDCON .7)
8) If desired, is the receive-enable bit (REN_0 or REN_1) set?
9) Is the serial port interrupt enabled?
10) Is the global interrupt-enable bit set?
17.6 High-Speed Microcontroller Does Not Work in Existing 8051 Design
Although the high-speed microcontroller family was designed as a drop-in replacement for the 8051
family, a developer may occasionally notice problems when inserting into an existing design. Often these
problems are related to slow memory interfaces that cannot keep up with the increased throughput of the
faster microcontroller. In addition, software-timing loops run faster, possibly changing program
operation. These and other effects are described in Application Note 56: The DS80C320 as a Drop-In
Replacement for the 8051/8032 Microcontroller and Application Note 57: DS80C320 Memory Interface
Timing.
Application Note 89: High-Speed Micro Memory Interface Timing discusses interfacing other members of
the high-speed microcontroller family to external memory.