Using External Reference; Using External Ram; Ram Recommendations; Ram Socket Pin Layout - Atmel megaAVR Getting Started

9.3.3 Using External
Reference
9.4 Using External
RAM
9.4.1 RAM
Recommendations
9.4.2 RAM Socket Pin
Layout
9.4.3

Address Latch

9.5 Using LCD
Connections
megaAVR™ Starter Kit Manual
header pins labeled "Analog Ref" and "Analog Gnd" in the previous diagram or from the
two holes marked Meter + and -.
To use the A/D converters with an external Voltage Reference, the link marked "LK1"
must be cut. The voltage is applied to the pins marked "Analog Ref" and "Analog Gnd"
on the Analog header—see previous diagram.
The ATmega103 can be used with external SRAM. A socket is provided for a 28-pin
RAM chip and for an address latch chip. These are next to the device adapter at the top
of the board. There is also a header for further memory expansion, which is connected
through the address latch. The pin functions are marked on the board, including chip
select (CS).
A low power 62256 SRAM is suggested with an access time of 70 nS. If a very fast RAM
is required, the crystal frequency may need to be increased. If a much slower SRAM is
used, the SRAM Wait State bit must be enabled in user software–—see data book. The
layout of the 28-pin RAM socket is shown below, and any RAM with this pin-out could
be used.
The board connections are for a 74HC573 device. This device will operate reliably with
the 4 MHz crystal supplied but if a faster crystal is inserted, a faster version of this
device may be required—74AHC573 or 74FHC573. Note that this option will alter the
EMC characteristics of the board and the CE mark will no longer be valid
without retesting.
The header marked LCD interface is for a standard 2 x 16 LCD. The connections are
shown on the board and in the following table.
Connection Name
0V
+5
Vo
RS
Wr
E
D0
A14 1 28 VCC
A12 2 27 WE
A7 3 26 A13
A6 4 25 A8
A5 5 24 A9
A4 6 23 A11
A3 7 22 OE
A2 8 21 A10
A1 9 20 CS
A0 10 19 I/O7
I/O0 11 18 I/O6
I/O1 12 17 I/O5
I/O2 13 16 I/O4
VSS 14 15 I/O3
Function
Ground
V - must be 5V
CC
Contrast
Register Select- A14
Not Write
Enable
Data Bit 0
Board Applications
9-3