Apb Subsystem (Peripheral Bus) - Siemens ERTEC 200P-2 Manual

WRAP4
INCR4
WRAP8
INCR8
WRAP16
INCR16
Address phase of transfer type BUSY
If the number of consecutive address phases at ARM926-D AHB port / ARM926-I AHB
port / AHB port without an IDLE cycle in between exceeds NR_ADDR_ARM926-D /
NR_ADDR_ARM926-I / in the AHB_BURSTBREAKER Register (see chap. 2.3.10.9.22,
configured by SW), the Burst Breaker will insert an IDLE cycle immediately if the current
transfer is SINGLE or INCR unspecified length. In the later case the INCR will be split. If
the current transfer is any kind of burst with specified length the IDLE insertion will be
done at the end of the ongoing burst transfer (to not interrupt any cache transfers).
NR_ADDR_ARM926-D/NR_ADDR_ARM926-I set to '0' means Burst Breaker at
ARM926-D AHB port/ARM926-I AHB port port is set to transparent mode. Any transfer is
passed through as is; no IDLE insertion.
If 0 < NR_ADDR_ARM926-D/NR_ADDR_ARM926-I < 255 IDLE insertion is activated for
the threshold defined by NR_ADDR_ARM926-D/ NR_ADDR_ARM926-I. Changes of
NR_ADDR_ARM926-D/ NR_ADDR_ARM926-I are updated at the next IDLE cycle.
Recommended is a value of 8 (max. 8er-Burst) for NR_ADDR_ARM926-D/
NR_ADDR_ARM926-I.

2.3.2.4 APB Subsystem (Peripheral Bus)

Only the AHB/APB bridge has a master function at the APB. All peripheral blocks of the
APB are operated as slaves. All peripheral function blocks with low performance require-
ments (e.g. not burst-compatible) are connected to the APB bus. The AHB/APB bridge
has a single-stage write buffer.
The following blocks are connected at the ERTEC 200P APB bus:
SCRB
Boot ROM
Timer 0-5
F-timer
Watchdog
4x UART
2x SPI
I²C
GPIO
HostIF (APB interface)
PerIF (APB interface)
I-filter
The APB bus is a 32-bit wide bus. The bus frequency is 125 MHz. The APB bus in the
ERTEC 200P has a wider functionality than the ARM-APB bus (see document /11/, 5.5).
Unlike the standard APB bus, it offers the option of variable timing (wait states) and byte
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Technical data subject to change
47 ERTEC 200P-2 Manual
Version 1.0