MC9S12T64 Datasheet, PDF (165/608 Pages) Motorola, Inc – Specification

Freescale Semiconductor, Inc.
Multiplexed External Bus Interface (MEBI)
Functional Description
• Advance and load from data bus — The queue shifts up one stage
with stage one being filled with the data on the read data bus.
Execution start status is valid when the E clock is low and is represented
by four states:
• No start — Execution of the current instruction continues.
• Start interrupt — An interrupt sequence has begun.
NOTE:
The start-interrupt state is indicated when an interrupt request or tagged
instruction alters program flow. SWI and TRAP instructions are part of
normal program flow and are indicated as start even or start odd
depending on their alignment. Since they are present in the queue, they
can be tracked in an external queue rebuild. An external event that
interrupts program flow is indeterministic. Program data is not present in
the queue until after the vector jump.
• Start even instruction — The current opcode is in the high byte of
stage three of the queue.
• Start odd instruction — The current opcode is in the low byte of
stage three of the queue.
Table 31 IPIPE[1:0] Decoding when E Clock is High
Data Movement
(capture at E fall)
0:0
0:1
1:0
1:1
Mnemonic
—
—
ALD
—
Meaning
No movement
Reserved
Advance queue and load from bus
Reserved
Table 32 IPIPE[1:0] Decoding when E Clock is Low
Execution Start
(capture at E rise)
0:0
0:1
1:0
1:1
Mnemonic
—
INT
SEV
SOD
Meaning
No start
Start interrupt sequence
Start even instruction
Start odd instruction
MOTOROLA
Multiplexed External Bus Interface (MEBI)
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MC9S12T64Revision 1.1.1
165