HD6432646 Hitachi, HD6432646 Datasheet - Page 589

• Manufacturer Part Number: HD6432646
• Description: (HD64F264x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

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.
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
Initial value:
Initial value:
UMSR
Note: *
R/W:
R/W:
Bit:
Bit:
Only 1 can be written, to clear the flag.
UMSR15 UMSR14 UMSR13 UMSR12 UMSR11 UMSR10
UMSR7
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
15
0
7
0
UMSR6
R/(W)*
R/(W)*
14
0
6
0
UMSR5
R/(W)*
R/(W)*
13
0
5
0
UMSR4
R/(W)*
R/(W)*
12
0
4
0
UMSR3
R/(W)*
R/(W)*
11
0
3
0
UMSR2
R/(W)*
R/(W)*
10
0
2
0
UMSR1
R/(W)*
UMSR9
R/(W)*
9
0
1
0
(Initial value)
(x = 15 to 0)
UMSR0
R/(W)*
UMSR8
R/(W)*
8
0
0
0
555