3.2
Signal Index
Table 1. System Bus Signal Index (Normal Operation)
Group
Signal Name
Mnemonic
Function
Address Bus
A27-A0
Lower 27 bits of address bus. (I/O)(1)
Address Bus/Byte Write
Enables
A31-A28
WE3-WE0
Upper four bits of address bus (I/O), or byte write enable
signals (O)(1) for accesses to external memory or peripherals.
Address
Identifies the processor state and the address space of the
current bus cycle. (I/O)
Function Codes
Data Bus 31 - 16
FC3-FC0
D31-D16
Upper 16-bit data bus used to transfer byte or word data.
Used in 16-bit bus mode. (I/O)
Data
Lower 16-bit data bus used to transfer 3-byte or long-word
data. (I/O)
Not used in 16-bit bus mode.
Data Bus 15 - 0
Parity 2 - 0
D15-D0
Parity signals for byte writes/reads from/to external memory
module. (I/O)
PRTY2-PRTY0
Parity
Parity signals for byte writes/reads from/to external memory
module or defines 16-bit bus mode. (I/O)
Parity 3/16BM
Parity Error
PRTY3/16BM
PERR
Indicates a parity error during a read cycle. (O)
Chip Select
Row Address Select 7
Interrupt Acknowledge 7
CS
RAS7
IACK7
Enables peripherals or DRAMs at programmed addresses (O)
or interrupt level 7 acknowledge line. (O)
Memory
Controller
Chip Select 6-0
Row Address Select 6-0
CS6-CS0
RAS6-RAS0
Enables peripherals or DRAMs at programmed addresses.
(O)
Column Address Select
3 - 0/Interrupt
Acknowledge 1, 2, 3, 6
CAS3-CAS0/
IACK6,3,2,1
DRAM column address select or interrupt level acknowledge
lines. (O)
Indicates that an external device requires bus mastership.
(I)(1)
Bus Request
BR
BG
Indicates that the current bus cycle is complete and the
QUICC has relinquished the bus. (O)
Bus Grant
Indicates that an external device has assumed bus
mastership. (I)
Bus Grand Acknowledge
BGACK
Bus Arbitration
Identifies the bus cycle as part of an indivisible
read-modify-write operation (I/O) or initial QUICC
configuration select. (I)
Read-Modify-Write Cycle
Initial Configuration 0
RMC
CONFIG0
Bus Clear Out/Initial
Configuration 1/Row
Address Select 2
Double-Drive
Indicates that an internal device requires the external bus
(Open-Drain O) or initial QUICC configuration select (I) or row
address select 2 double-drive output. (O)
BCLRO/CONFIG1/
RAS2DD
6
TS68EN360
2113B–HIREL–06/05