GR740-UM-DS, Nov 2017, Version 1.7
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GR740
13.4.7 AMBA interface
The AMBA interface consists of an APB interface, an AHB master interface and DMA FIFOs. The
APB interface provides access to the user registers, which are described in section 13.4.8. The DMA
engines have 32-bit wide FIFOs to the AHB master interface, which are used when reading and writ-
ing to the bus.
The transmitter DMA engine reads data from the bus in bursts, which are half the FIFO size in length.
A burst is always started when the FIFO is half-empty or if it can hold the last data for the packet. The
burst containing the last data might have a shorter length if the packet is not an even number of bursts
in size.
The receiver DMA works in the same way except that it checks if the FIFO is half-full and then per-
forms a burst write to the bus which is half the FIFO size in length. Byte accesses are used for non-
word-aligned buffers and/or packet lengths that are not a multiple of four bytes. There can be there-
fore 1 to 3 single byte writes when writing the beginning and the end of a received packet.
13.4.7.1 APB slave interface
As mentioned above, the APB interface provides access to the user registers, which are 32-bits wide.
Accesses to this interface are required to be aligned word accesses. The result is undefined if this
restriction is violated.
0
1
1
1
0
1
Write, incre-
menting
address, ver-
ify before
writing, no
acknowledge
Executed normally. Length must
be 4 or less. Otherwise nothing is
done. Same alignment restric-
tions apply as for rmw. If they
are violated nothing is done. No
reply is sent.
0
1
1
1
1
0
Write, single
address, ver-
ify before
writing, send
acknowledge
Executed normally. Length must
be 4 or less. Otherwise nothing is
done and error code is set to 9.
Same alignment restrictions
apply as for rmw. If they are vio-
lated nothing is done and error
code is set to 10. If an AHB error
occurs error code is set to 1.
Reply is sent.
0
1
1
1
1
1
Write, incre-
menting
address, ver-
ify before
writing, send
acknowledge
Executed normally. Length must
be 4 or less. Otherwise nothing is
done and error code is set to 9.
Same alignment restrictions
apply as for rmw. If they are vio-
lated nothing is done and error
code is set to 10. If an AHB error
occurs error code is set to 1.
Reply is sent.
1
0
-
-
-
-
Unused
Stored to DMA-channel.
1
1
-
-
-
-
Unused
Stored to DMA-channel.
Table 153.
AMBA port hardware RMAP handling of different packet type and command fields.
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Command
Action
Reserved
Command
/ Response
Write /
Read
Verify
data
before
write
Acknow-
ledge
Increment
Address