Overview
9-7
External Memory Interface
Table 9–1. EMIF Signal Descriptions
6
2
0
1
6
7
0
1
6
2
0
2
6
2
1
1 Pin
(I/O/Z)
Description
n n n n
CLKOUT1
O
Clock output. Runs at the CPU clock rate.
n n n n
CLKOUT2
O
Clock output. Runs at 1/2 the CPU clock rate. Used for synchronous memory
interface on ’C6202
n
BUSREQ
O
Active high bus request signal
n
ECLKOUT
O
EMIF clock output. All EMIF I/O are clocked relative to ECLKOUT.
n
ECLKIN
I
EMIF clock input. Must be provided by system.
n n n n
ED[31:0]
I/O/Z
Data I/O. 32-bit data input/output from external memories and peripherals
n n n n
EA[21:2]
O/Z
External address output. Drives bits 21–2 of the byte address.
n n n n
CE0
O/Z
Active low chip select for memory space CE0
n n n n
CE1
O/Z
Active low chip select for memory space CE1
n n n n
CE2
O/Z
Active low chip select for memory space CE2
n n n n
CE3
O/Z
Active low chip select for memory space CE3
n n n n
BE[3:0]
O/Z
Active low byte enables. Individual bytes and halfwords can be selected for both
read and write cycles. Decoded from two LSBs of the byte address.
n n n n
ARDY
I
Ready. Active low asynchronous ready input used to insert wait states for
slow memories and peripherals.
n n n
M AOE
O/Z
Active low output enable for asynchronous memory interface
n n n
M AWE
O/Z
Active low write strobe for asynchronous memory interface
n n n
M ARE
O/Z
Active low read strobe for asynchronous memory interface
n n
M M SSADS
O/Z
Active low address strobe/enable for SBSRAM interface
n n
M M SSOE
O/Z
Output buffer enable for SBSRAM interface
n n
M M SSWE
O/Z
Active low write enable for SBSRAM interface
n n
SSCLK
O/Z
SBSRAM interface clock. Programmable to either the CPU clock rate or half
of the CPU clock rate.
n n
M M SDRAS
O/Z
Active low row strobe for SDRAM memory interface
n n
M M SDCAS
O/Z
Active low column strobe for SDRAM memory interface
n n
M M SDWE
O/Z
Active low write enable for SDRAM memory interface
n n n
SDA10
O/Z
SDRAM A10 address line. Address line/autoprecharge disable for SDRAM
memory.
n n
SDCLK
O/Z
SDRAM interface clock. Runs at 1/2 the CPU clock rate. Equivalent to
CLKOUT2.
n n n n
HOLD
I
Active low external bus hold (3-state) request
n n n n
HOLDA
O
Active low external bus hold acknowledge
† ’M’ indicates a multiplexed output signal