DBGDTRTX_EL0: Debug Data Transfer Register, Transmit

Purpose

Transfers data from the PE to an external debugger. For example, it is used by a debug target to transfer data to the debugger. See DBGDTR_EL0 for additional architectural mappings. It is a component of the Debug Communication Channel.

Configuration

External register DBGDTRTX_EL0 bits [31:0] are architecturally mapped to AArch64 System register DBGDTRTX_EL0[31:0].

External register DBGDTRTX_EL0 bits [31:0] are architecturally mapped to AArch32 System register DBGDTRTXint[31:0].

DBGDTRTX_EL0 is in the Core power domain.

Attributes

DBGDTRTX_EL0 is a 32-bit register.

Field descriptions

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Return DTRTX

Bits [31:0]

Return DTRTX.

Reads of this register:

If TXfull is set to 1, return the last value written to DTRTX.
If TXfull is set to 0, return an UNKNOWN value.

After the read, TXfull is cleared to 0.

Writes to this register:

If TXfull is set to 1, set DTRTX to UNKNOWN.
If TXfull is set to 0, update the value in DTRTX.

After the write, TXfull remains unchanged.

For the full behavior of the Debug Communications Channel, see 'The Debug Communication Channel and Instruction Transfer Register'.

The reset behavior of this field is:

On a Cold reset, this field resets to an architecturally UNKNOWN value.

Accessing DBGDTRTX_EL0

If EDSCR.ITE == 0 when the PE exits Debug state on receiving a Restart request trigger event, the behavior of any operation issued by a DTR access in memory access mode that has not completed execution is CONSTRAINED UNPREDICTABLE, and must do one of the following:

It must complete execution in Debug state before the PE executes the restart sequence.
It must complete execution in Non-debug state before the PE executes the restart sequence.
It must be abandoned. This means that the instruction does not execute. Any registers or memory accessed by the instruction are left in an UNKNOWN state.

DBGDTRTX_EL0 can be accessed through the external debug interface:

Component	Offset	Instance
Debug	0x08C	DBGDTRTX_EL0

This interface is accessible as follows:

When DoubleLockStatus(), or !IsCorePowered(), or OSLockStatus() or !AllowExternalDebugAccess(), accesses to this register generate an error response.
When SoftwareLockStatus(), accesses to this register are RO.
Otherwise, accesses to this register are RW.