Signal Description
5-2
MC68030 USER’S MANUAL
MOTOROLA
NOTE
In this section and in the remainder of the manual,
assertion
and
negation
are used to specify forcing a signal to a particular
state. In particular, assertion and assert refer to a signal that is
active or true; negation and negate indicate a signal that is inac-
tive or false. These terms are used independently of the voltage
level (high or low) that they represent.
5.1 SIGNAL INDEX
The input and output signals for the MC68030 are listed in Table 5-1. Both the names and
mnemonics are shown along with brief signal descriptions. For more detail on each signal,
refer to the paragraph in this section named for the signal and the reference in that
paragraph to a description of the related operations.
Guaranteed timing specifications for the signals listed in Table 5-1 can be found in
M68030EC/D,
MC68030 Electrical Specifications
.
Table 5-1. Signal Index (Sheet 1 of 2)
Signal Name Mnemonic Function
Function Codes FC0–FC2 3-bit function code used to identify the address space of each bus cycle.
Address Bus A0–A31 32-bit address bus.
Data Bus D0–D31 32-bit data bus used to transfer 8, 16, 24, or 32 bits of data per bus cycle.
Size SIZ0/SIZ1 Indicates the number of bytes remaining to be transferred for this cycle.
These signals, together with A0 and A1, define the active sections of the
data bus.
Operand Cycle Start OCS
Identical operation to that of ECS except that OCS is asserted only
during the first bus cycle of an operand transfer.
External Cycle Start ECS
Provides an indication that a bus cycle is beginning.
Read/Write R/W
Defines the bus transfer as a processor read or write.
Read-Modify-Write Cycle RMC
Provides an indicator that the current bus cycle is part of an indivisible
read-modify-write operation.
Address Strobe AS
Indicates that a valid address is on the bus.
Data Strobe DS
Indicates that valid data is to be placed on the data bus by an external
device or has been placed on the data bus by the MC68030.
Data Buffer Enable DBEN
Provides an enable signal for external data buffers.
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