C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 138

• Manufacturer Part Number: C505_9708
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Each element of the message control register is made of two complementary bits. This special
mechanism allows to selectively set or reset specific elements (leaving others unchanged) without
requiring read-modify-write cycles. None of these elements will be affected by reset.
Table 6-6 below shows how to use and interpret these 2-bit fields.
Table 6-6 : Set/Reset Bits
Value of
the 2-bit Field
CAN Message Control Register Low MCR0 (Address F7n0 H )
CAN Message Control Register High MCR1 (Address F7n1 H )
Bit
MSGVAL
TXIE
RXIE
INTPND
Semiconductor Group
F7n1 H
0
0
1
1
F7n0 H
Bit No.
0
1
0
1
MSB
Function on Write
reserved
Reset element
Set element
Leave element unchanged
7
Function
Message valid
Indicates, if the corresponding message object is valid or not. The CAN controller
only operates on valid objects. Message objects can be tagged invalid, while they
are changed, or if they are not used at all.
Transmit interrupt enable
Defines, if bit INTPND is set after successful transmission of a frame.
Receive interrupt enable
Defines, if bit INTPND is set after successful reception of a frame.
Interrupt pending
Indicates, if this message object has generated an interrupt request (see TXIE
and RXIE), since this bit was last reset by the microcontroller, or not.
RMTPND
MSGVAL
rw
rw
6
5
TXRQ
TXIE
rw
rw
4
6-76
Meaning on Read
reserved
Element is reset
Element is set
reserved
3
CPUUPD
On-Chip Peripheral Components
MSGLST
RXIE
rw
rw
2
1
NEWDAT
INTPND
rw
rw
Reset Value : UU H
Reset Value : UU H
0
C505C Only
LSB
1)
1997-08-01
MCR0
MCR1