AT89C51CC03C_14 Datasheet, PDF (1/7 Pages) ATMEL Corporation – PCA – Incorect Behavior with CPU X2 Mode Bit of HSB

Active Errata List
• CAN – Sporadic Errors
• PCA – Incorect Behavior with CPU X2 Mode Bit of HSB
• Timer0/1 – Extra Interrupt
• Transmission after a 3 bit Intermessage
Errata History
Lot Number
all lots from A02543
Errata List
1, 2, 3, 4
Errata Description
1. CAN – Sporadic Errors
When BRP = 0 or when BRP > 0 and SMP = 0, the CAN controller may desyn-
chronize and send one error frame to ask for the retransmission of the incoming
frame, even though it had no error.
This is likely to occur with BRP = 0 or after long inter frame periods without syn-
chronization (low bus load). The CAN macro can still properly synchronize on
frames following the error.
Workaround
Setting BRP greater than 0 in CANBT1 and SMP equals 1 in CANBT3 allows re-
synchronization with the majority vote, and thus fixes the issue.
The sampling point might have to be slightly advanced for the majority vote to take
place within the bit. Therefore, at maximum speed of 1Mbit/s, the sampling point
should be at less than 80% (e.g. 75%) for XTAL = 16 MHz or less than 85% (e.g.
80%) for XTAL = 20 MHz.
CAN
Microcontrollers
AT89C51CC03
AT89C51CC03C
AT89C51CC03U
Errata Sheet
2. PCA – Incorect Behavior with CPU X2 Mode Bit of HSB
When starting the microcontroller in X2 mode upon reset with the X2 fuse bit of
the HSB, the PCA may not work properly when configured with Timer0 in X1
mode as clock input.
Workaround
Set the CPU in X2 mode by software by writing CKCON register at the begin of
the application.
3. Timer0/1 – Extra Interrupt
When Timer0 is in X1 mode and Timer1 in X2 mode and vice versa, extra inter-
rupt may randomly occur for Timer0 or Timer1.
Workaround
Use the same mode for the two timers.
4. Transmission after a 3 bit Intermessage
If a Transmit Message Object (MOB) is enabled while the CAN bus is busy with
an on going message, the transmitter will wait for the 3-bit Intermission before
starting its transmission. This is in full agreement with the CAN recommendation.
4293G–CAN–06/05
1