C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 151

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

Special Function Register SYSCON (Address B1 H )
Bit
CMOD
The software Initialization is enabled by setting bit INIT in the control register. This can be done by
the microcontroller via software, or automatically by the CAN controller on a hardware reset, or if the
EML switches to busoff state.
While INIT is set
Setting bit CCE in addition, allows to change the configuration in the bit timing register.
For initialization of the CAN Controller, the following actions are required:
If a message object is not needed, it is sufficient to clear its message valid bit (MSGVAL), ie. to
define it as not valid. Otherwise, the whole message object has to be initialized.
After the initialization sequence has been completed, the microcontroller clears the INIT bit.
Now the BSP synchronizes itself to the data transfer on the CAN bus by waiting for the occurrence
of a sequence of 11 consecutive recessive bits (ie. bus idle) before it can take part in bus activities
and start message transfers.
Semiconductor Group
– all message transfer from and to the CAN bus is stopped
– the CAN bus output TXDC is “1” (recessive)
– the control bits NEWDAT and RMTPND of the last message object are reset
– the counters of the EML are left unchanged.
– configure the bit timing register (CCE required)
– set the Global Mask Registers
– initialize each message object.
B1 H
Bit No. MSB
7
–
The functions of the shaded bits are not described here.
Function
Prescaler selection for CAN controller
Control bit for CAN controller input clock selection. The time quantum (t q )
of the CAN controller timing is affected by this (and hecne the baudrate).
CMOD = 0 : The ÷ 2 prescaler is enabled (reset value).
CMOD = 1 : The ÷ 2 prescaler is disabled.
This bit must be cleared when f
6
–
EALE RMAP CMOD
5
4
6-89
3
On-Chip Peripheral Components
osc
is over 10 MHz.
2
–
XMAP1
1
Reset Value : XX100X01 B
XMAP0
LSB
0
C505C Only
SYSCON
1997-08-01