JTAG_AddDeviceReadCmd

Adds a read command to the internal command buffer associated with a device. This enables a programmer to build up a sequence of commands i.e. write, read and write/read before executing the sequence of commands. The internal command buffer has a size of 131070 bytes (128 kB).

FTC_STATUS

JTAG_AddDeviceReadCmd

(FTC_HANDLE ftHandle, BOOL bInstructionTestData, DWORD dwNumBitsToRead, DWORD dwTapControllerState)

Parameters

ftHandle	Handle of the device.
bInstructionTestData	Selects the instruction register (TRUE) or the test register (FALSE) to write data to.
dwNumBitsToRead	Number of bits to be read from the external device. Valid range is 2 to 524280.
dwTapControllerState	State that the Test Access Port (TAP) controller will be left in.

Return Value
FTC_SUCCESS if successful, otherwise the return value is one of the following FTC error codes:

   FTC_INVALID_HANDLE
   FTC_INVALID_NUMBER_BITS
   FTC_INVALID_TAP_CONTROLLER_STATE
   FTC_COMMAND_SEQUENCE_BUFFER_FULL



Remarks
Do not invoke JTAG_Write, JTAG_READ or JTAG_WriteRead functions while constructing a sequence of commands as this will clear the sequence of commands and associated data from the internal command buffer.

This command can be used with multiple devices connected. If only one device is connected, JTAG_AddReadCmd may be used instead.

Calling this function is equivalent to adding the commands and data from a JTAG_Read call to the internal command buffer.

This function can be used with JTAG_ClearDeviceCmdSequence, JTAG_AddDeviceWriteCmd, JTAG_AddDeviceWriteReadCmd and JTAG_ExecuteCmdSequence to buffer a long list of commands and data which can then be sent to the FT2232C in one go. This can provide faster data transfer rates in some applications.