SAM7S512_14 Datasheet, PDF (339/775 Pages) ATMEL Corporation – ARM-based Flash MCU

Notes: 1. When SVACC is low, the state of SVREAD becomes irrelevant.
2. TXRDY is reset when data has been transmitted from TWI_THR to the shift register and set when this data has been
acknowledged or non acknowledged.
30.9.5.2 Write Operation
The write mode is defined as a data transmission from the master.
After a START or a REPEATED START, the decoding of the address starts. If the slave address is decoded,
SVACC is set and SVREAD indicates the direction of the transfer (SVREAD is low in this case).
Until a STOP or REPEATED START condition is detected, TWI stores the received data in the TWI_RHR register.
If a STOP condition or a REPEATED START + an address different from SADR is detected, SVACC is reset.
Figure 30-25 on page 339 describes the Write operation.
Figure 30-25. Write Access Ordered by a Master
SADR does not match,
TWI answers with a NACK
SADR matches,
TWI answers with an ACK
Read RHR
TWD
RXRDY
SVACC
SVREAD
EOSVACC
S ADR W NA DATA NA P/S/Sr SADR W A DATA A
A DATA NA S/Sr
SVREAD has to be taken into account only while SVACC is active
Notes: 1. When SVACC is low, the state of SVREAD becomes irrelevant.
2. RXRDY is set when data has been transmitted from the shift register to the TWI_RHR and reset when this data is read.
30.9.5.3 General Call
The general call is performed in order to change the address of the slave.
If a GENERAL CALL is detected, GACC is set.
After the detection of General Call, it is up to the programmer to decode the commands which come afterwards.
In case of a WRITE command, the programmer has to decode the programming sequence and program a new
SADR if the programming sequence matches.
Figure 30-26 on page 339 describes the General Call access.
Figure 30-26. Master Performs a General Call
0000000 + W
RESET command = 00000110X
WRITE command = 00000100X
TXD
GCACC
SVACC
S GENERAL CALL ^A Reset or write DADD ^A DATA1 ^{A DATA2 A New SADR A P}
New SADR
Programming sequence
Reset after read
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
339