APB Read Debug Service

Reads a specified number of bytes from the fabric APB bus to the specified MSS RAM area. The operation makes the required number of read transactions using the selected transaction size, APBDWSIZE.

The addressed fabric peripheral generates an error or fail to respond within a user-defined window, in that case any subsequent transfers are aborted and corresponding error flags are returned.

Table 1. APB Read Debug Service Request
System Service Descriptor Bit Field	Value	Description
15:7	MBOXADDR[10:2]	Mailbox address. See Table 2.
6:0	77H	APB Read Debug service command.

The following table lists the APB Read Debug Service mailbox format.

Table 2. APB Read Debug Service Mailbox Format
Offset	Length (bytes)	Parameter	Direction	Description
0	4	APBADDR[28:0]	Input	Specifies the target address and transfer size for the APB write and APB read operations.
4	1	APBDWSIZE[1:0]	Input	Specifies the data transfer size to be used by the APB write and APB read operations.
8	2	MAXBYTES[11:0]	Input	Calculates specified number of bytes from the fabric APB bus to the Shared Buffer. Number of bytes = MAXBYTES + 1.
16	8	MSSADDR	Input	Specifies the MSS RAM area where to copy MAXBYTES+1 of the APB Read data to. Note that all accesses are done with MSS User privileges.