27.3.2 Managing ABUSes
The ABUSes of an APORT are shared resources. The user needs to be mindful of this in assigning I/O for different clients throughout
the chip, as it is possible to have conflicts for a given ABUS. Each ABUS has an arbiter responsible for limiting the control over the
ABUS to one and only one client. If multiple clients attempt to control an ABUS, the arbiter allows no client control over the ABUS and
asserts a conflict signal to the clients. The user has the ability to check for such a conflict in each client's status, as well as generate an
interrupt.
Having only one client control an ABUS is not the same as having only one user of an ABUS. It is possible for multiple clients to access
a single ABUS, but requires all but one client to relinquish control of the ABUS. To do this, some clients have bits to disable bus master-
ship which are 0 by default. One example is the BUSXMASTERDIS bit in the ACMPn_CTRL. When set to 1, the client will not assert
control of the ABUS switches, but may still connect to an ABUS that is controlled by another client.
For example, if an IDAC, ADC, and ACMP all want to use the same pin on a particular ABUS the user might set the bus master disable
bit to 1 for the IDAC and ACMP. The ADC is the sole master of the switch configuration on that ABUS, so switches are configured using
the configuration set in the ADC.
ACMP0
ABUS[0]
ABUS[2]
ABUS[4]
ABUS[6]
ABUS[1]
ABUS[3]
ABUS[5]
ABUS[7]
ACMP1
ADC0
APORT_CONTROL
ABUS_REQ =
0000_1111
ABUS_REQ =
0011_0000
ABUS_REQ =
1000_0000
Figure 27.3. APORT Example 1
Figure 27.3 APORT Example 1 on page 924
illustrates the sharing of APORT. For illustration purposes, each ABUS is identified by a
numeric index (instead of APAX, APAY, APBX, etc.). Also, the requests from all the APORT clients are packed into a bit-vector named
BUS_REQ to illustrate the request from the APORT Clients (instead of by name such as BUS1XREQ, BUS1YREQ, BUS2XREQ, etc.).
In
Figure 27.3 APORT Example 1 on page 924
, ABUS and client are the same color if the client has been granted the ABUS.
In
Figure 27.3 APORT Example 1 on page 924
ADC0 has requested ABUS[3:0], ACMP1 has requested ABUS[5:4], ACMP0 has re-
quested ABUS[7], and ABUS[6] is unused. No APORT Client has requested the same ABUS as another, so there is no conflict.
EFM32JG1 Reference Manual
APORT - Analog Port
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