AT91SAM7A2-EK Evaluation Board User Guide
3-5
6115B–ATARM–10-May-05
3.8
Crystal
Oscillators and
Clock
Distribution
The system clock is derived from a 6 MHz crystal oscillator mounted on board. The on-
chip PLL-based frequency multiplier results in a master clock at 30 MHz. A 32 kHz crys-
tal oscillator is used for the low-power mode and the Watchtimer module.
3.9
Memory
Organization
The Flash memory is an AT49BV1614A (1Mx16-bit). Write-protection for half of the on-
board Flash memory is provided. Output 4 of Jumper J15 drives the address pin 20 of
the Flash.
To access the whole memory, close jumper J15: 3 - 4.
To protect the upper memory and access only the lower memory (from 0x40000000 to
0x40080000: only 1 Mbyte), close jumper J15: 4 - 5.
The mapping defined by the boot software is shown in Table 3-7.
3.10
I/O Expansion
Two I/O expansion connectors provide the users with the general-purpose I/O (GPIO)
lines, analog lines, VDD and ground. The jumper J10 (DIS) can be used to disconnect
application board features, such as the buzzer or RS-232 drivers. The connectors are
not fitted at the factory; however, the user can fit any 25 x 2 connector on a 0.1" (2.54
mm) pitch. Figure 4-9 shows the connector pin-out.
3.11
External Bus
Interface
Figure 4-7 shows one AT49BV1614A with a 2 Mbyte 16-bit Flash and a 512 Kbyte 16-bit
SRAM device.
Figure 4-7 also shows the bus expansion connector that, like the I/O expansion connec-
tor, is not fitted at the factory. The user can fit any 32 x 2 connector on a 0.1" (2.54 mm)
pitch to gain access to the data, address, chip select, read/write, oscillator output and
wait state pins. VDD and ground are available on the connector.
On-board jumpers (J13, J14 and J15) allow the users to connect Chip Selects either to
on-board memories or to the expansion connector.
In most case, jumpers should be set up as follows:
!
Close J13: 2 - 3. On-board SRAM chip select is driven by NCS1.
!
Close J15: 3 - 4. On-board Flash address line 20 is driven. Users can access the
whole memory space.
Others are left open.
Table 3-7. Memory Mapping
Element
Address
Flash
0x40000000
SRAM
0x48000000
Summary of Contents for AT91SAM7A2-EK
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