ST STM32F301 6 Series Reference Manual page 848

Debug support (DBG)
Further details of the SW-DP state machine can be found in the Cortex
and the CoreSight™ Design Kit r0p1TRM.
28.8.4 DP and AP read/write accesses
•
Read accesses to the DP are not posted: the target response can be immediate (if
ACK=OK) or can be delayed (if ACK=WAIT).
•
Read accesses to the AP are posted. This means that the result of the access is
returned on the next transfer. If the next access to be done is NOT an AP access, then
the DP-RDBUFF register must be read to obtain the result.
The READOK flag of the DP-CTRL/STAT register is updated on every AP read access
or RDBUFF read request to know if the AP read access was successful.
•
The SW-DP implements a write buffer (for both DP or AP writes), that enables it to
accept a write operation even when other transactions are still outstanding. If the write
buffer is full, the target acknowledge response is "WAIT". Except for IDCODE read, or
CTRL/STAT read, or ABORT write, which are accepted even if the write buffer is full.
•
Because of the asynchronous clock domains SWCLK and HCLK, two extra SWCLK
cycles are needed after a write transaction (after the parity bit) to make the write
effective internally. These cycles should be applied while driving the line low (IDLE
state)
This is particularly important when writing the CTRL/STAT for a power-up request. If the
next transaction (requiring a power-up) occurs immediately, it fails.
28.8.5 SW-DP registers
Access to these registers is initiated when APnDP=0
A(3:2)
00 Read
00 Write
01 Read/Write
01 Read/Write
10 Read
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Table 120. SW-DP registers
CTRLSEL bit
R/W of SELECT
register
-
-
0
1
-
RM0366 Rev 5
Register
The manufacturer code is not set to ST code
IDCODE
0x2BA01477 (identifies the SW-DP)
ABORT
Purpose is to:
– request a system or debug power-up
– configure the transfer operation for AP
DP- accesses
CTRL/STAT
– control the pushed compare and pushed
verify operations.
– read some status flags (overrun, power-
up acknowledges)
Purpose is to configure the physical serial
WIRE
port protocol (like the duration of the
CONTROL
turnaround time)
Enables recovery of the read data from a
READ
corrupted debugger transfer, without
RESEND
repeating the original AP transfer.
RM0366
®
-M4F r0p1 TRM
Notes
-