AT89LP828 Atmel Corporation, AT89LP828 Datasheet - Page 84
AT89LP828
Manufacturer Part Number
AT89LP828
Description
Manufacturer
Atmel Corporation
Datasheet
1.AT89LP428.pdf
(149 pages)
Specifications of AT89LP828
Flash (kbytes)
8 Kbytes
Max. Operating Frequency
25 MHz
Cpu
8051-1C
Max I/o Pins
30
Spi
1
Uart
1
Sram (kbytes)
0.75
Eeprom (bytes)
1024
Self Program Memory
IAP
Operating Voltage (vcc)
2.4 to 5.5
Timers
3
Isp
SPI/OCD
Watchdog
Yes
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84
AT89LP428/828
Figure 16-2. Mode 0 Waveforms
Mode 0 may be used as a hardware accelerator for software emulation of serial interfaces such
as a half-duplex Serial Peripheral Interface (SPI) in mode (0,0) or (1,1) or a Two-wire Interface
(TWI) in master mode. An example of Mode 0 emulating a TWI master device is shown in
16-3. In this example, the start, stop, and acknowledge are handled in software while the byte
transmission is done in hardware. Falling/rising edges on TXD are created by setting/clearing
SM2. Rising/falling edges on RXD are forced by setting/clearing the P3.0 register bit. SM2 and
P3.0 must be 1 while the byte is being transferred.
Figure 16-3. UART Mode 0 TWI Emulation (SMOD1 = 1)
Mode 0 transfers data LSB first whereas SPI or TWI are generally MSB first. Emulation of these
interfaces may require bit reversal of the transferred data bytes. The following code example
reverses the bits in the accumulator:
Write to SBUF
SMOD1 = 0
SM2 = 0
SMOD1 = 1
SM2 = 0
SMOD1 = 0
SM2 = 1
SMOD1 = 1
SM2 = 1
(SDA) RXD
(SCL) TXD
EX:
REVRS: RLC
SM2
P3.0
TI
RXD (RX)
RXD (RX)
RXD (RX)
RXD (RX)
RXD (TX)
RXD (TX)
RXD (TX)
RXD (TX)
MOV
XCH
RRC
XCH
DJNZ R7, REVRS
TXD
TXD
TXD
TXD
R7, #8
A
A, R6
A
A, R6
0
0
0
0
0
0
0
1
0
0
; C << msb(ACC)
; msb(ACC) >> B
1
1
2
1
1
1
1
1
1
3
2
2
2
2
2
2
2
2
4
3
3
3
3
3
3
3
3
5
4
4
4
4
4
4
4
4
6
5
5
Sample ACK
5
5
5
5
5
5
7
6
6
6
6
6
6
6
6
ACK
3654A–MICRO–8/09
7
7
7
7
7
7
7
7
Figure