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Rainbow Electronics T89C51CC01 User Manual

Page 81

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81

T89C51CC01

Rev. D – 17-Dec-01

15.9 Time Trigger
Communication (TTC)
and Message Stamping

The T89C51CC01 has a programmable 16-bit Timer (CANTIMH&CANTIML) for mes-
sage stamp and TTC.

This CAN Timer starts after the CAN controller is enabled by the ENA bit in the CANG-
CON register.

Two modes in the timer are implemented:

Time Trigger Communication:

Capture of this timer value in the CANTTCH & CANTTCL registers on Start
Of Frame (SOF) or End Of Frame (EOF), depending on the SYNCTTC bit in
the CANGCON register, when the network is configured in TTC by the TTC
bit in the CANGCON register.

Note:

In this mode, CAN only sends the frame once, even if an error occurs.

Message Stamping

Capture of this timer value in the CANSTMPH & CANSTMPL registers of the
message object which received or sent the frame.

All messages can be stamps.

The stamping of a received frame occurs when the RxOk flag is set.

The stamping of a sent frame occurs when the TxOk flag is set.

The CAN Timer works in a roll-over from FFFFh to 0000h which serves as a time base.

When the timer roll-over from FFFFh to 0000h, an interrupt is generated if the ETIM bit
in the interrupt enable register IEN1 is set.

Figure 38. Block diagram of CAN Timer

EOF on CAN frame

ENA

CANGCON.1

CANTCON

RXOK i

CANSTCH.5

TXOK i

CANSTCH.4

÷

6

Fcan

CLOCK

SOF on CAN frame

TTC

CANGCON.5

SYNCTTC

CANGCON.4

CANTTCH & CANTTCL

CANSTMPH & CANSTMPL

CANTIMH & CANTIML

OVRTIM

CANGIT.5

When 0xFFFF to 0x0000