6.4 Transfer Fast Data (XferFastData) Pseudo Operation

oData = XferFastData (iData)

• To quickly send 32 bits of data in/out of the device.

1. The TMS Header is clocked into the device to select the Shift DR state.
   Note: For Two-Wire (4-phase) – On the last clock, the oPrAcc bit is shifted out on TDO while clocking in the TMS header. If the value of oPrAcc is not ‘1’, the whole operation must be repeated.
2. The input value of the PrAcc bit, which is ‘0’, is clocked in.
   Note: For Two-Wire (4-phase) – The TDO during this operation will be the LSb of output data. The rest of the 31 bits of the input data are clocked in and the 31 bits of output data are clocked out. For the last bit of the input data, the TMS Footer = 1 is set.

3. TMS Footer = 10 is clocked in to return the TAP controller to the Run/Test Idle state.

• The SendCommand (ETAP_FASTDATA) must be sent first to select the Fast Data register, as shown in SendCommand (ETAP_FASTDATA)). See Table 20-3 for detailed descriptions of commands.
  Note: The 2-phase XferData is only used when talking to the PE. See Programming Executive for more information.

• The following is an example of how to use the Transfer Fast Data (XferFastData) function:

  // Select the Fastdata Register
  SendCommand(ETAP_FASTDATA)
  // Send/Receive 32-bit Data
  oData = XferFastData(32’h0x12)