Материал: DOC1228

The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a positive pulse. The bit codings are shown in Table 43.

When pulsing WR or OE, the command loaded determines the action executed. The command is a byte where the different bits are assigned functions as shown in Table 44.

Figure 76. Parallel Programming

ATmega161

+5V

RDY/BSY PD1

VCC

OE PD2

PB7 - PB0 DATA

WR PD3

BS1 PD4

XA0 PD5

XA1 PD6

PAGEL PD7

+12 V RESET

PA0

XTAL1

GND

Table 42. Pin Name Mapping

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Table 44. Command Byte Bit Coding

A. Load Command “Write Flash”

1.Set XA1, XA0 to “10”. This enables command loading.

2.Set BS1 to “0”.

3.Set DATA to “0001 0000”. This is the command for Write Flash.

4.Give XTAL1 a positive pulse. This loads the command.

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B. Load Address Low Byte

1.Set XA1, XA0 to “00”. This enables address loading.

2.Set BS1 to “0”. This selects low address.

3.Set DATA = Address low byte ($00 - $FF).

4.Give XTAL1 a positive pulse. This loads the address low byte.

C. Load Data Low Byte

1.Set BS1 to “0”. This selects low data byte.

2.Set XA1, XA0 to “01”. This enables data loading.

3.Set DATA = Data low byte ($00 - $FF).

4.Give XTAL1 a positive pulse. This loads the data byte.

D. Latch Data Low Byte

Give PAGEL a positive pulse. This latches the data low byte. (See Figure 77 for signal waveforms.)

E. Load Data High Byte

1.Set BS1 to “1”. This selects high data byte.

2.Set XA1, XA0 to “01”. This enables data loading.

3.Set DATA = Data high byte ($00 - $FF).

4.Give XTAL1 a positive pulse. This loads the data byte.

F. Latch Data High Byte

Give PAGEL a positive pulse. This latches the data high byte.

G. Repeat “B” through “F” 64 times to fill the page buffer.

To address a page in the Flash, seven bits are needed (128 pages). The five most significant bits are read from address high byte as described in section “H” below. The two least significant page address bits, however, are the two most significant bits (bit7 and bit6) of the latest loaded address low byte as described in section “B”.

H. Load Address High byte

1.Set XA1, XA0 to “00”. This enables address loading.

2.Set BS1 to “1”. This selects high address.

3.Set DATA = Address high byte ($00 - $1F).

4.Give XTAL1 a positive pulse. This loads the address high byte.

I. Program Page

1.Give WR a negative pulse. This starts programming of the entire page of data. RDY/BSYgoes low.

2.Wait until RDY/BSY goes high.

(See Figure 78 for signal waveforms.)

J. End Page Programming

1.Set XA1, XA0 to “10”. This enables command loading.

2.Set DATA to “0000 0000”. This is the command for No Operation.

3.Give XTAL1 a positive pulse. This loads the command, and the internal write signals are reset.

K. Repeat “A” through “J” 128 times or until all data have been programmed.

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ATmega161(L)

Figure 77. Programming the Flash Waveforms

XA1

XA2

BS1

XTAL1

WR

RDY/BSY

RESET +12V

OE

BS2

PAGEL

Figure 78. Programming the Flash Waveforms (Continued)

XA1

XA0

BS1

XTAL1

WR

RDY/BSY

RESET +12V

OE

PAGEL

BS2

Programming the EEPROM The programming algorithm for the EEPROM data memory is as follows (refer to “Programming the Flash” for details on command, address and data loading):

1.A: Load Command “0001 0001”.

2.H: Load Address High Byte ($00 - $01)

3.B: Load Address Low Byte ($00 - $FF)

4.E: Load Data Low Byte ($00 - $FF)

L: Write Data Low Byte

1.Set BS to “0”. This selects low data.

2.Give WR a negative pulse. This starts programming of the data byte. RDY/BSY goes low.

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3.Wait until to RDY/BSY goes high before programming the next byte. (See Figure 79 for signal waveforms.)

The loaded command and address are retained in the device during programming. For efficient programming, the following should be considered:

•The command needs to be loaded only once when writing or reading multiple memory locations.

•Address high byte only needs to be loaded before programming a new 256-word page in the EEPROM.

•Skip writing the data value $FF, that is, the contents of the entire EEPROM after a Chip Erase.

These considerations also apply to Flash, EEPROM and Signature bytes reading.

Figure 79. Programming the EEPROM Waveforms

1.A: Load Command “0000 0010”.

2.H: Load Address High Byte ($00 - $1F)

3.B: Load Address Low Byte ($00 - $FF)

4.Set OE to “0”, and BS1 to “0”. The Flash word low byte can now be read at DATA.

5.Set BS to “1”. The Flash word high byte can now be read at DATA.

6.Set OE to “1”.

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