MC68HC912B32MFU8 MOTOROLA [Motorola, Inc], MC68HC912B32MFU8 Datasheet - Page 103

• Manufacturer Part Number: MC68HC912B32MFU8
• Description: 16-Bit Microcontroller
• Manufacturer: MOTOROLA [Motorola, Inc]

BSVR — BDLC State Vector Register
I0, I1, I2, I3 — Interrupt Source
MC68HC912B32
MC68HC912B32TS/D
RESET:
Decreases the CPU overhead associated with servicing interrupts while operating a serial communica-
tion protocol. It provides an index offset that is directly related to the BDLC’s current state.
Source of the pending interrupt request. Bits are encoded according to Table 35.
Bits I0, I1, I2, and I3 are cleared by a read of the BSVR register except when the BDLC data register
needs servicing (RDRF, RXIFR, or TDRE conditions). RXIFR and RDRF can only be cleared by a read
of the BSVR register followed by a read of BDR. TDRE can either be cleared by a read of the BSVR
register followed by a write to the BDLC BDR register, or by setting the TEOD bit in BCR2.
Upon receiving a BDLC interrupt, the user may read the value within the BSVR, transferring it to the
CPU’s index register. The value can be used to index a jump table to access a service routine. For ex-
ample:
NOP instructions are used to align the JMP instructions onto 4-byte boundaries so that the value in the
BSVR may be used intact. Each of the service routines must end with an RTI instruction.
BSVR
$0C
$1C
$00
$04
$08
$10
$14
$18
$20
Bit 7
0
0
SERVICE
*
*
JMPTAB
I3
0
0
0
0
0
0
0
0
1
I2
0
0
0
0
1
1
1
1
0
6
0
0
LDX
JMP
JMP
NOP
JMP
NOP
JMP
NOP
.
.
.
JMP
END
I1
0
0
1
1
0
0
1
1
0
I3
5
0
Table 35 Interrupt Sources
I0
0
1
0
1
0
1
0
1
0
BSVR
JMPTAB,X
SERVE0
SERVE1
SERVE2
SERVE8
I2
4
0
Tx data register empty (TDRE)
Symbol invalid or out of range
Rx data register full (RDRF)
Received IFR byte (RXIFR)
No Interrupts Pending
I1
3
0
Loss of arbitration
Interrupt Source
Fetch State Vector Number
Enter service routine,
(must end in an RTI)
Service condition #0
Service condition #1
Service condition #2
Service condition #8
Received EOF
CRC error
Wakeup
I0
2
0
1
0
0
Bit 0
0
0
8 (highest)
0 (lowest)
Priority
MOTOROLA
1
2
3
4
5
6
7
$00F9
103