PORT A INTERFACE
4 - 4
PORT A
MOTOROLA
Decoding in such a way simplifies connection to high-speed random-access memories
EXTERNAL
ADDRESS BUS
SWITCH
EXTERNAL
ADDRESS BUS
A0 - A15
X ADDRESS (XA)
Y ADDRESS (YA)
PROGRAM ADDRESS (PA)
16 - BIT INTERNAL
ADDRESS BUSES
16
EXTERNAL
DATA BUS
SWITCH
EXTERNAL
DATA BUS
D0 - D23
X DATA (XD)
Y DATA (YD)
PROGRAM DATA (PD)
24 - BIT INTERNAL
DATA BUSES
24
GLOBAL DATA (GD)
EXTERNAL
BUS CONTROL
LOGIC
BUS CONTROL SIGNALS
RD –- READ ENABLE
WR – WRITE ENABLE
PS – PROGRAM MEMORY SELECT
DS – DATA MEMORY SELECT
X/Y – X MEMORY/Y MEMORY SELECT
BN –- BUS NEEDED
BR – BUS REQUEST
BG – BUS GRANT
WT – BUS WAIT
BS – BUS STROBE
Figure 4-1 Port A Signals
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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