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I'm working with a customer that has a custom board using the MSP432E4 device. They intentionally did not use an external crystal connected to OSC0/OSC1. Our documentation states that this is okay as long as OSC0 is connected to ground, as it is on the customer's custom board. The device is factory new without having been programmed previously.
In this configuration, we cannot "Connect to Target" successfully. We get:
CS_DAP_0: Error connecting to the target: (Error -613 @ 0x0) The target indicates that it is busy. Either try the SWD request again, or abort the transaction. (Emulation package 9.11.0.00128)
This is despite the "Test Connection" fully succeeding.
In suspicion that this may have had something to do with not having a crystal, I took the MSP0ESP432E401Y development kit to try and reproduce the issue. I started with a working configuration, which worked with both SWD and 4-wire JTAG mode. Next I removed the crystal from the board and tied OSC0 to ground. Now I can fully reproduce the issue my customer is facing. It doesn't matter if I use SWD or 4-wire JTAG mode.
The Using SimpleLink MSP432E4 microcontrollers over the JTAG interface document seems to me to state that a crystal should not be required. Here are the troubleshooting steps.
If the JTAG IR and DR integrity scan-test succeeds, the device core is out of reset and may not have initialized itself. If, however, the integrity scan-test fails, the issue is in the power up process. Perform the following steps to make sure every known cause is eliminated and to find the source of the issue:
The device datasheet also states that an external crystal is not required.
How can we get CCS to successfully "Connect to Target" when not providing an external crystal on OSC0/OSC1 and connecting OSC0 to ground?
Thanks,
Stuart
Hi Stuart,
I think you are referring to this post which is not yet resolved. https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1306547/msp432e411y-swd-communication-error-though-msp432e411y-jtag-pin. I have yet to understand why it does not connect without the MOSC.
I'm working with a customer that has a custom board using the MSP432E4 device. They intentionally did not use an external crystal connected to OSC0/OSC1. Our documentation states that this is okay as long as OSC0 is connected to ground, as it is on the customer's custom board. The device is factory new without having been programmed previously
That is correct. Unused OSC0 can be tied to GND.
In suspicion that this may have had something to do with not having a crystal, I took the MSP0ESP432E401Y development kit to try and reproduce the issue. I started with a working configuration, which worked with both SWD and 4-wire JTAG mode. Next I removed the crystal from the board and tied OSC0 to ground. Now I can fully reproduce the issue my customer is facing. It doesn't matter if I use SWD or 4-wire JTAG mode.
Can you run a test connection? What does it show? Below is my scan-test log.
How can we get CCS to successfully "Connect to Target" when not providing an external crystal on OSC0/OSC1 and connecting OSC0 to ground?
By default, the device starts with the internal PIOSC. MOSC is not needed.
5.2.5.1 Fundamental Clock Sources
There are multiple clock sources for use in the microcontroller. The Run and Sleep Mode
Configuration Register (RSCLKCFG) can be used to configure the required clock source for the
device after Power-On Reset, as well as the system clock divisor encodings. The available clock
sources are as follows:
■ Precision Internal Oscillator (PIOSC). The precision internal oscillator is an on-chip clock
source that the microcontroller uses during and following POR. It is the clock source in effect at
the start of reset vector fetch and the start of code application execution. It does not require the
use of any external components and provides a clock that is 16 MHz ±FPIOSC across temperature
(see Table 27-19 on page 1837). The PIOSC allows for a reduced system cost in applications that
require an accurate enough clock source.
Hi Stuart,
Although TM4C123 and TM4C129/MSP432E are two different MCUs, I think the architecture of the clock system is similar. Both uses PIOSC to startup the device. Both states in the datasheet that if crystal is not used, OSC0 can be tied to GND.
What is your TCK frequency? Can you try lowering the TCK frequency and does it make a difference?
Can you also show the customer's schematic for the JTAG interface?
Hi Stuart,
You brought up a good point about the Ethernet ROM bootloader. The Ethernet ROM bootloader will need the 25Mhz MOSC in order to run the integrated PHY. Perhaps without the 25Mhz MOSC, the PHY is not running and causes the Ethernet ROM bootloader to get stuck. In the TM4C129 errata, a 4.7k resistor is recommended for RBIAS connection to GND. However, the schematic shown by the customer was using 4.87k as if Ethernet is to be used. I don't know if that makes a difference. Perhaps, worth swapping out 4.87k for 4.7k with 10% tolerance to see if that makes a difference.
