Mitsubishi DS5000TK, DS907x SIP manual Unable to Invoke Stop Mode, Serial Port does not Work

USER'S GUIDE

lithium batteries have a very long time constant. Putting the device on the shelf for one to two weeks may restore enough voltage to battery back the memory again. The lifetime of such a battery will be reduced, however.

Crystal is not running

Check the capacitance used with the crystals. Approxi- mately 20±40 pF is typical. Take note of any stray capacitance that could increase the actual loading.

UNABLE TO INVOKE STOP MODE

Unlike the 8051, the STOP bit in the PCON register is Timed Access protected. Existing 8051 code will not use the Timed Access procedure, so the STOP mode would not be successfully invoked.

Memory map is not configured

If the developer has not used the Bootstrap Loader to select the correct memory map, it may be incompatible with the software. For example, a DS2251 with 64K of memory could be configured with a 32K range. Code above 32K in NV RAM would not be executed.

SERIAL PORT DOES NOT WORK

The serial port is not a complicated peripheral, but there are many elements that need to be initialized. The fol- lowing checklist is provided to help in debugging.

1.Are the P3.0 (RXD) and P3.1 (TXD) bits in the Port 3 SFR latch set to 1?

2.Is the correct serial port mode selected?

3.If using serial port mode 1 or 3, is appropriate timer reload value selected?

4.If using serial port mode 1 or 3, is timer 1 enabled? (TCON.6)

5.If desired, is the serial port doubler bit, SMOD, set? (PCON.7)

6.If desired, is the receiver enable bit, REN, set? (SCON.4)

7.Is the serial port interrupt bit, ES, set? (IE.4)

8.Is the global interrupt enable bit, EA, set? (IE.7)

PROGRAM WILL NOT EXECUTE

This is a general category of complaint. In most cases more information is needed. Prior to calling for applica- tions support, check the status of ALE, PSEN, XTAL2, Ports, and RST. Also, try adding instructions that write a value to the ports to see which sections of code are being run and which are not (similar to using print state- ments). The following is a list of some common reasons that the program will not execute.

EA is floating

The EA pin has an internal pull down resistor. If EA is allowed to float, it assumes an active state which pre- vents using NV RAM. When EA=0, the device will use the Expanded Bus on Ports 0 and 2. Connect EA directly to +5V for proper operation.

No Stack

C programmers frequently use a large memory model. This places the C stack in MOVX RAM area. The typical default address for compilers is to place the stack at 0000h. A device in a Partitionable mode will not have MOVX NV RAM begin at 0000h. The C start up configu- ration should be altered to put the stack and any other data variables above the Partition. C programs will typi- cally crash if there is no stack.

Code is written for an 8052

The 8052 family has 256 bytes of on chip RAM and a third timer. Secure Microcontroller family devices are 8051 derivatives and do not have these resources.

Watchdog is running and unsupported

If the Watchdog is enabled but not supported by soft- ware, it will reset the microprocessor at intervals of

122.8ms with a 12 MHz crystal. If writing to an LCD dis- play or similar activity, the initialization may take more time that this. The code would appear not to run since the display would never get it message printed. Make certain the Watchdog is either supported or disabled in software.

The CRC bit is set on a DS5001

If the CRC bit is set, the DS5001 CPU will invoke the Bootstrap Loader on each power up and perform a CRC. If the answer does not match the stored value, the processor will remain in the loader mode. If the user has inadvertently set this bit and is not actually using the CRC, it will surely be incorrect and will invoke the loader on each power up. A program will seem to run (the inter- nal ROM checking the NV RAM) then stop.

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