ETAS
Hardware Description
FETK-T1.1
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User
Guide
24
4.7
Data Access
4.7.1
Calibration Data Access
The FETK-T1.1 is a serial FETK using DAP and a trace interface as the primary
microcontroller interface. Typical of all serial ETKs, XETKs and FETKs, the RAM
used for data emulation and data measurement is not accessible by the FETK
until the microcontroller is powered up and the startup handshake is per
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formed.
Serial FETKs use the ETAS two page concept, consisting of both a Reference
and a Working page.
The Reference Page is located in the ECU flash and can not be modified by a
simple write access. All changes to the Reference Page must be done via Flash
programming.
The Working Page is located within the microcontroller's ED RAM. The Working
Page may be a portion of or the entire size of the ED RAM. The ED RAM used
for the emulation of calibration data must not be used by the ECU software
directly as general purpose RAM. It is recommended that the ED RAM is perma
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nently powered by the FETK-T1.1 or ECU and shall not be reseted by the ECU, if
the FETK-T1.1 signals a permanently powering of the ED RAM during hand
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shake.
The FETK / INCA has the complete control over the RAM used as Working Page
and it's contents. When enabling data emulation, the FETK establishes a basic
start-up configuration of the data in the Working Page by copying the corre
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sponding data in the Flash to the emulation space.
To enable calibration, the Working Page must be activated. The process of
switching from the Reference Page to the Working Page and vice versa is
known as page switching.
The FETK-T1.1 supports Protocol Based page switching for all supported
microcontroller. Page switching is done in microcontroller software by switch
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ing the overlay memory on (Working Page) and off (Reference Page) using
microcontroller overlay registers. The FETK-T1.1 does not directly control the
microcontroller overlay registers. Instead the FETK-T1.1 and microcontroller
software use a simple communication method with a shared mailbox in RAM.
The FETK-T1.1 uses this mailbox to request and monitor page switching; the
microcontroller software is responsible to service this mailbox and perform the
page switches. Using an overlay modification description, also in RAM, the
FETK-T1.1 provides the necessary information.
The FETK-T1.1 can access both the Reference Page and the Working Page,
regardless of which is active from the microcontroller’s point of view.
Another important restriction is that no access to the memory is possible, while
the ECU is not running. To enable a cold start measurement in spite of this
restriction, the cold start measurement procedure is defined to give the user
the feeling of a parallel FETK.