Signal Index - Motorola MC68030 User Manual

Signal Description
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 .
Signal Name
Function Codes
Address Bus
Data Bus
Size
Operand Cycle Start
External Cycle Start
Read/Write
Read-Modify-Write Cycle
Address Strobe
Data Strobe
Data Buffer Enable
5-2
NOTE
Table 5-1. Signal Index (Sheet 1 of 2)
Mnemonic
FC0–FC2 3-bit function code used to identify the address space of each bus cycle.
A0–A31 32-bit address bus.
D0–D31 32-bit data bus used to transfer 8, 16, 24, or 32 bits of data per bus cycle.
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.
OCS Identical operation to that of ECS except that OCS is asserted only
during the first bus cycle of an operand transfer.
ECS Provides an indication that a bus cycle is beginning.
R/W Defines the bus transfer as a processor read or write.
RMC Provides an indicator that the current bus cycle is part of an indivisible
read-modify-write operation.
AS Indicates that a valid address is on the bus.
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.
DBEN Provides an enable signal for external data buffers.
MC68030 USER'S MANUAL
Function
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