Visible to Intel only — GUID: iga1405458017391
Ixiasoft
Visible to Intel only — GUID: iga1405458017391
Ixiasoft
12.4.4.2. Control Register
Embedded software controls the JTAG UART core's interrupt generation and reads status information via the control register. The Control Register Bits table below describes the function of each bit.
Bit(s) | Name | Access | Description |
---|---|---|---|
0 | RE | R/W | Interrupt-enable bit for read interrupts. |
1 | WE | R/W | Interrupt-enable bit for write interrupts. |
8 | RI | R | Indicates that the read interrupt is pending. |
9 | WI | R | Indicates that the write interrupt is pending. |
10 | AC | R/C | Indicates that there has been JTAG activity since the bit was cleared. Writing 1 to AC clears it to 0. |
[32:16] | WSPACE | R | The number of spaces available in the write FIFO. |
A read from the control register returns the status of the read and write FIFOs. Writes to the register can be used to enable/disable interrupts, or clear the AC bit.
The RE and WE bits enable interrupts for the read and write FIFOs, respectively. The WI and RI bits indicate the status of the interrupt sources, qualified by the values of the interrupt enable bits (WE and RE). Embedded software can examine RI and WI to determine the condition that generated the IRQ. See the Interrupt Behavior section for further details.
The AC bit indicates that an application on the host PC has polled the JTAG UART core via the JTAG interface. Once set, the AC bit remains set until it is explicitly cleared via the Avalon® interface. Writing 1 to AC clears it. Embedded software can examine the AC bit to determine if a connection exists to a host PC. If no connection exists, the software may choose to ignore the JTAG data stream. When the host PC has no data to transfer, it can choose to poll the JTAG UART core as infrequently as once per second. Delays caused by other host software using the JTAG download cable could cause delays of up to 10 seconds between polls.