AT90CAN128-16AE ATMEL Corporation, AT90CAN128-16AE Datasheet - Page 29

• Manufacturer Part Number: AT90CAN128-16AE
• Description: 8-bit Avr Microcontroller With 128K Bytes of Isp Flash And CAN Controller.flash (Kbytes) 128 Vcc (V) 2.7-5.5 EEPROM (Kbytes) 4 SRAM (bytes) 4K CAN (mess. Obj.) 15
• Manufacturer: ATMEL Corporation

XMEM Register Description
External Memory Control
Register A – XMCRA
4250C–CAN–03/04
Figure 16. External Data Memory Cycles with SRWn1 = 1 and SRWn0 = 0
System Clock (CLK
Note:
Figure 17. External Data Memory Cycles with SRWn1 = 1 and SRWn0 = 1
Note:
• Bit 7 – SRE: External SRAM/XMEM Enable
Writing SRE to one enables the External Memory Interface.The pin functions AD7:0,
A15:8, ALE, WR, and RD are activated as the alternate pin functions. The SRE bit over-
System Clock (CLK
Bit
Read/Write
Initial Value
DA7:0 (XMBK = 0)
DA7:0 (XMBK = 1)
DA7:0 (XMBK = 0)
DA7:0 (XMBK = 1)
1. SRWn1 = SRW11 (upper sector) or SRW01 (lower sector), SRWn0 = SRW10 (upper
1. SRWn1 = SRW11 (upper sector) or SRW01 (lower sector), SRWn0 = SRW10 (upper
DA7:0
A15:8
CPU
DA7:0
A15:8
ALE
WR
RD
CPU
ALE
WR
RD
sector) or SRW00 (lower sector).
The ALE pulse in period T6 is only present if the next instruction accesses the RAM
(internal or external).
)
sector) or SRW00 (lower sector).
The ALE pulse in period T7 is only present if the next instruction accesses the RAM
(internal or external).
)
Prev. addr.
Prev. data
Prev. data
Prev. data
Prev. addr.
Prev. data
Prev. data
Prev. data
SRE
R/W
7
0
T1
T1
SRL2
R/W
6
0
Address
Address
Address
T2
Address
Address
SRL1
Address
R/W
XX
T2
5
0
XX
Address
T3
SRL0
Data
Data
Data
R/W
4
0
Address
T3
Data
Data
Data
SRW11
T4
R/W
3
0
T4
SRW10
R/W
2
0
T5
AT90CAN128
SRW01
T5
R/W
1
0
T6
SRW00
R/W
0
0
(1)
(1)
T6
T7
XMCRA
29