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15.2.16 Unread Message Status Register (UMSR)
The unread message status register (UMSR) is a 16-bit readable/writable register containing status
flags that indicate, for individual mailboxes (buffers), that a received message has been
overwritten by a new receive message before being read. If a previously received message is
overwritten by a newly received message, the old data will be lost.
UMSR
Bit:
Initial value:
R/W:
Bit:
Initial value:
R/W:
Note: *
Only 1 can be written, to clear the flag.
Bits 15 to 0—Unread Message Status Flags (UMSRx): Status flags indicating that an unread
receive message has been overwritten.
Bit x: UMSRx
0
1
15
14
UMSR7
UMSR6
UMSR5
0
0
R/(W)*
R/(W)*
R/(W)*
7
6
UMSR15 UMSR14 UMSR13 UMSR12 UMSR11 UMSR10
0
0
R/(W)*
R/(W)*
R/(W)*
Description
[Clearing condition]
Writing 1
Unread receive message is overwritten by a new message
[Setting condition]
When a new message is received before RXPR is cleared
13
12
11
UMSR4
UMSR3
0
0
0
R/(W)*
R/(W)*
5
4
3
0
0
0
R/(W)*
R/(W)*
10
9
UMSR2
UMSR1
UMSR0
0
0
R/(W)*
R/(W)*
R/(W)*
2
1
UMSR9
UMSR8
0
0
R/(W)*
R/(W)*
R/(W)*
(Initial value)
(x = 15 to 0)
8
0
0
0
555
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