Ahb Burst Breaker; Table 7: Ahb Master-Slave Coupling - Siemens ERTEC 200P-2 Manual

TCM92
AHB mas-
ter
ARM926-
*)
D
*)
ARM926-I
GDMA
Host inter-
face
PN-IP M1
PN-IP M2
*) Burst access by the AHB master can be interrupted with the AHB burst breaker.
Important:
To avoid prolonged blocks during slave access, the AHB masters must not arbitrate a
slave for too long. Arbitration could for example take too long if the ARM926-D master
had too many transactions with the EMC slave in its write buffer. Another master (e.g.
host interface or PN-IP-M1) would then be blocked from accessing the EMC slave during
this time and would have to wait in "wait" until the ARM926-D master released the EMC
slave.
The ARM926-D and ARM926-I masters have burst breakers fitted at the AHB access
point. A burst breaker generates an idle phase for a clock after a configured number of
consecutive address phases (see 2.3.2.3.3). A different AHB master can then be as-
signed the AHB slave during this idle phase. This is possible because re-arbitration at an
AHB slave can only be carried out if a master releases that AHB slave (idle phase).
The PN-IP-M1/2 and GDMA AHB masters cannot occupy a slave for longer than one
burst sequence of 8 data transfers. At the end of this sequence, the AHB master then
always implements an idle phase. A different AHB master can therefore always be as-
signed the given slave at the end of an 8-beat burst sequence. This limit is fixed for the
PN-IP-M1/2 AHB master, but can be set per DMA job for the GDMA AHB master. The
host interface AHB master can only implement single transactions at the AHB.

AHB Burst Breaker

2.3.2.3.3
To improve the real-time capabilities of ERTEC 200P three Burst Breakers are used to
prevent ARM926-D and ARM926-I to block resources by consecutive burst transfers
without IDLE cycles in between, which are necessary for re-arbitration of AHB masters.
The Burst Breaker counts the address phases of following ARM926-D/ARM926-I AHB
transfers:
SINGLE
INCR unspecified length
Copyright © Siemens AG 2016. All rights reserved
Technical data subject to change
D- ETB ARM- GDM
ICU A
6
x x x
x x x
x x
x

Table 7: AHB Master-slave coupling

46
EMC AHB/APB PerIF
bridge host
x x x
x x
x x x
x x x
x
PerIF- PN-IP
PN
x
x
x
ERTEC 200P-2 Manual
Version 1.0