SERIAL I/O
11.4 Clock asynchronous serial I/O (UART) mode
11.4.8 Sleep mode
This mode is used to transfer data between the specified microcomputers, which are connected by using
UARTi. The sleep mode is selected by setting the sleep select bit (bit 7 at addresses 3016, 3816 and B016
)
to “1” when receiving.
In the sleep mode, receive operation is performed when the MSB (D
8
when the transfer data = 9-bit length,
D
7
when it is 8-bit length, D when it is 7-bit length) of the receive data is “1.” Receive operation is not
6
performed when the MSB is “0.” (The UARTi receive register’s contents are not transferred to the UARTi
receive buffer register. Additionally, the receive complete flag and each error flag do not change, and no
UARTi receive interrupt request occurs.)
The following shows an usage example of the sleep mode when the transfer data = 8-bit length.
✕ Be sure to set the same transfer data format for the master and slave microcomputers. Additionally, be
sure to select the sleep mode for the slave microcomputers.
✕ Then, transmit the data, of which structure is as follows, from the master microcomputer:
• Bit 7 = “1”
• Bits 6 to 0 indicate the address of the slave microcomputer to be communicated
✕ Each slave microcomputer receives the data described in step ✕. (At this time, a UARTi receive interrupt
request occurs.)
✕ Be sure to check for each slave microcomputer, in the interrupt routine, whether bits 6 to 0 of the receive
data match its own address.
✕ For the slave microcomputer of which address matches bits 6 to 0 of the receive data, terminate the
sleep mode. (Do not terminate the sleep mode for the other slave microcomputers.)
By performing steps ✕ to ✕, “the microcomputer which performs transfer” is specified.
✕ Transmit the data of which bit 7 = “0” from the master microcomputer. (Only one slave microcomputer
specified in steps ✕ to ✕ can receive this data. The other microcomputers do not receive this data.)
✕ By repeating step ✕, continuous transfer can be performed between two specific microcomputers. When
communicating with another slave microcomputer, perform steps ✕ to ✕ in order to specify the new
slave microcomputer.
Data is transferred between the master
microcomputer and one specific slave microcomputer
selected from multiple slave microcomputers.
Master
Slave A
Slave B
Slave C
Slave D
Fig. 11.4.14 Sleep mode
7905 Group User’s Manual Rev.1.0
11-54
RENESAS [ RENESAS TECHNOLOGY CORP ]
