Copyright © Siemens AG 2016. All rights reserved
48
ERTEC 200P-2 Manual
Technical data subject to change
Version 1.0
enables. Wait state and byte enable capability is achieved by introducing sideband sig-
nals. This allows byte-by-byte access to peripherals.
The APB modules allow the following types of access:
APB mod-
ule
Access per-
mitted
Comment
SCRB
Only 32-bit *) Data bus: 32-bit
Boot ROM
8/16/32-bit
Data bus: 32-bit
Host inter-
face (XHIF)
Only 32-bit
Data bus: 32-bit
UART
16/32-bit
Data bus: 16-bit, i.e. the top 16 bits are ignored
F-timer
Only 32-bit
Data bus: 32-bit
Timer 0-5
Only 32-bit
Data bus: 32-bit
Watchdog
Only 32-bit
Data bus: 32-bit
I2C
8/16/32-bit
Data bus: 8-bit, i.e. the top 24 bits are ignored
SPI
16/32-bit
Data bus: 16-bit, i.e. the top 16 bits are ignored
GPIO
Only 32-bit
Data bus: 32-bit
I-filter
8/16/32-bit
Data bus: 32-bit
Peripheral
interface
8/16/32-bit
Data bus: 32-bit
SCRB
Only 32-bit
Data bus: 32-bit
*) Handling of access over APB within the modules varies. Please see the module specifications/section on the relevant module.
Note:
Burst access (INCR, INCR4, INCR8, INCR16, WRAP, WRAP4, WRAP8, WRAP16) is
allowed; access is split into single instances of access at the APB by the AHB2APB
bridge.
The AHB/APB bridge is implemented between the two buses. The AHB/APB bridge has a
single-stage write buffer.
The function of the AHB bridge is detailed in document /40/ AHB_APB_BRIDGE_V1.0-
pdf.
Important:
Write access to APB modules in the AHB2APB bridge is posted. Additional clocks are
also required at the APB bus until write access is "effective" in the APB register/RAM.
Subsequent read/write access via
another
data path (e.g. AHB) can therefore overtake
the previous APB write access.
If this is to be prevented, the "effectiveness" of the APB write access must be ensured in
the relevant APB register/RAM with a subsequent instance of APB read access to the
same APB address. The following write/read access may only be implemented after that
APB read access.
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