Difference between revisions of "J-Link OB SAM3U NordicSemi"
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== Supported baudrates == |
== Supported baudrates == |
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− | This J-Link OB supports max. 1 MBaud. The |
+ | This J-Link OB supports max. 1 MBaud. The internal divider is calculated as follows: |
+ | Div = (((2 * OS_FSYS) / BaudrateHz * 16) + 1) / 2; |
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− | xxx |
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− | '''Note:''' The real baudrate and the selected one should not deviate more than 3% |
+ | '''Note:''' The real baudrate and the selected one should not deviate more than 3% to guarantee proper communication on VCOM. |
== Pin driving policy == |
== Pin driving policy == |
Revision as of 17:24, 4 July 2018
Contents
VCOM functionality
This J-Link model supports VCOM.
Supported baudrates
This J-Link OB supports max. 1 MBaud. The internal divider is calculated as follows:
Div = (((2 * OS_FSYS) / BaudrateHz * 16) + 1) / 2;
Note: The real baudrate and the selected one should not deviate more than 3% to guarantee proper communication on VCOM.
Pin driving policy
The following pins are available on this OB:
- OB_Tx (driven by J-Link OB)
- OB_Rx (driven by target)
- CTS (driven by target. LOW == Target ready to receive data)
- RTS (driven by J-Link OB. LOW == J-Link OB ready to receive data)
J-Link OB starts driving its VCOM output pins as soon as it receives a "set baudrate" command. This command is send by the PC as soon as a COM port is opened. Unfortunately, there is no specific command / packet etc. send by the PC in case a COM port is opened. Therefore the "set baudrate" approach is the only one to detect COM port activity.
J-Link OB stops driving the RTS pin if J-Link OB detects that hardware flow control is not used on the target side.
Hardware flow control support
Hardware flow control is supported by this J-Link OB. By default, J-Link detects at runtime if the target uses flow control or not. This is done as follows:
- If CTS is detected as HIGH (Target not ready) before the first character is sent by J-Link OB, the pin is assumed to be not used by the target and flow control on the J-Link side gets disabled (CTS is ignored from now on, J-Link stops driving RTS)
Force or disable hardware flow control
It is possible to configure J-Link OB to bypass the hardware flow control auto-detection in the firmware and assume that hardware flow control is always or never used. This can be done via J-Link Commander and the following command:
J-Link>SetHWFC Enable/Disable/Force
- Enable: Default. Enables hardware flow control and runtime auto-detection
- Disable: Disables hardware flow control (never used)
- Force: Enables hardware flow control and bypasses runtime auto-detection (RTS is kept driven and CTS is kept sampling)