ST92150CV1Q-Auto STMicroelectronics, ST92150CV1Q-Auto Datasheet - Page 416

• Manufacturer Part Number: ST92150CV1Q-Auto
• Description: 8-bit MCU for automotive
• Manufacturer: STMicroelectronics

Specifications of ST92150CV1Q-Auto

• Internal Memory: Single Voltage FLASH up to 256 Kbytes, RAM up to 8Kbytes, 1K byte E3 TM (Emulated EEPROM)
• Minimum Instruction Time: 83 ns (24 MHz int. clock)

ST92124xxx-Auto/150xxxxx-Auto/250xxxx-Auto
KNOWN LIMITATIONS (Cont’d)
Workaround 1
The workaround is to replace any occurrence of
by
x=0 for the CAN_0 cell
x=1 for the CAN_1 cell
y=0 for the Receive FIFO 0
y=1 for the Receive FIFO 1
Explanation of Workaround 1
First, we need to make sure no interrupt can occur
between the test and the release of the FIFO to
avoid any added delay.
The workaround checks if the first 2 FIFO levels
are already full (FMP = 2) as the problem happens
only in this case.
If FMP≠2 we release the FIFO immediately, if
FMP=2, we monitor the reception status of the
cell.
The reception status is available in the CMSR reg-
ister bit 5 (REC bit).
Note: The REC bit was called RX in olders ver-
sions of the datasheet.
If the cell is not receiving, then REC bit in CMSR is
at 0, the software can release the FIFO immedi-
ately: there is no risk.
If the cell is receiving, it is important to make sure
the release of the mailbox will not happen at the
416/430
1
spp (CANx_CTRL_PG);
CANx_CTRL_CRFRy |= CRFR_rfom;
spp(CANx_CTRL_PG);
if ((CANx_CTRL_CRFRy & 0x03) == 0x02)
while (( CANx_CTRL_CMSRy & 0x20) && (CANx_CTRL_CDGRy & 0x08));
CANx_CTRL_CRFRy |= CRFR_rfom;
:
:
time when the received message is loaded into the
FIFO.
We could simply wait for the end of the reception,
but this could take a long time (200µs for a 100-bit
frame at 500kHz), so we also monitor the Rx pin of
the microcontroller to minimize the time the appli-
cation may wait in the while loop.
We know the critical window is located at the end
of the frame, 6+ CAN bit times after the acknowl-
edge bit (exactly six full bit times plus the time from
the beginning of the bit to the sample point). Those
bits represent the acknowledge delimiter + the end
of frame slot.
We know also that those 6+ bits are in recessive
state on the bus, therefore if the CAN Rx pin of the
device is at ‘0’, (reflecting a CAN dominant state
on the bus), this is early enough to be sure we can
release the FIFO before the critical time slot.
Therefore, if the device hardware pin Rx is at 0
and there is a reception on going, its message will
be transferred to the FIFO only 6+ CAN bit times
later at the earliest (if the dominant bit is the ac-
knowledge) or later if the dominant bit is part of the
message.