Assembly code example - master transmitter mode, Figure 52, In figure 52 t – Rainbow Electronics ATmega163L User Manual
Page 76: Ee figure 52), Table 52, Atmega163(l)
ATmega163(L)
76
Figure 52. Formats and States in the Master Transmitter Mode
Assembly Code Example - Master Transmitter Mode
;The slave being addressed has address 0x64. The code examples also assumes some sort of error handling
routine named ERROR.
;Part specific include file and TWI include file must be included.
; <Initialize registers, including TWAR, TWBR and TWCR>
ldi
r16, (1<<TWSTA) | (1<<TWEN)
out
TWCR, r16
; Send START condition
wait1:
in
r16,TWCR
; Wait for TWINT flag set. This indicates that
sbrs
r16,TWINT
; the START condition has been transmitted
S
SLA
W
A
DATA
A
P
$08
$18
$28
S
SLA
W
$10
A
P
$20
P
$30
A or A
$38
A
Other master
continues
A or A
$38
Other master
continues
R
A
$68
Other master
continues
$78
$B0
To corresponding
states in slave mode
MT
MR
Successfull
transmission
to a slave
receiver
Next transfer
started with a
repeated start
condition
Not acknowledge
received after the
slave address
Not acknowledge
received after a data
byte
Arbitration lost in slave
address or data byte
Arbitration lost and
addressed as slave
DATA
A
n
From master to slave
From slave to master
Any number of data bytes
and their associated acknowledge bits
This number (contained in TWSR) corresponds
to a defined state of the 2-Wire Serial Bus