Edit

Share via

Registry Settings for the Serial Service

  • Article

This topic describes the registry settings that Serial applies to all serial devices for which Serial is the function driver or a lower-level device filter driver.

Note

This topic describes programming traditional COM ports. For information on USB attached serial ports, see USB serial driver (Usbser.sys).

Serial queries the service entry values after it is loaded. If an entry value is not present, Serial adds the service entry value. Serial sets the entry value to the default value that is statically defined in the system-supplied Serial.sys driver. If a service entry value is changed after Serial is loaded, the new value is used the next time Serial is loaded.

Serial uses the following service entry values that are under the ..\Services\Serial registry key:

For general information on how to locate and work with Windows drivers registry keys, see Registry Trees for Devices and Drivers.

ForceFifoEnable (REG_DWORD)
Specifies a Boolean flag that indicates whether to force Serial to use FIFOs. If ForceFifofEnable is nonzero, FIFOs are used, regardless of whether Serial can detect the presence of FIFOs. Otherwise, FIFOs are used only if Serial can detect them. The default value of is nonzero. If the entry value is not present, Serial sets a ForceFifoEnable entry value to the default value. For more information about the method of detection, see the Serial driver sample on GitHub.

RxFIFO (REG_DWORD)
Specifies the number of bytes in the receive FIFO that triggers a port interrupt. For valid values, see the constants defined in the Serial.h header file in the Serial driver sample on GitHub. The default value of RxFIFO is eight bytes. If the entry value is not present, Serial sets an RxFIFO entry value to the default value.

TxFIFO (REG_DWORD)
Specifies the number of bytes in the transmit FIFO that triggers a port interrupt. For valid values, see the constants defined in the Serial.h header file in the Serial driver sample on GitHub. The default value of TxFIFO is 14 bytes. If the entry value is not present, Serial sets a TxFIFO entry value to the default value.

PermitShare (REG_DWORD)
Specifies a Boolean flag that indicates whether to permit the system to share the interrupt that a port uses. If PermitShare is nonzero, the interrupt can be shared; otherwise, the interrupt cannot be shared. The default value of PermitShare is 0x00000000. If the entry value is not present, Serial sets a PermitShare entry value to the default value.

BreakOnEntry, DebugLevel, and LogFifo
Specify entry values that are used for debugging. For more information about these entry values, see the Serial sample code that is included in the WDK.