SN8F2280 Series
USB 2.0 Full-Speed 8-Bit Micro-Controller
13.6.4 General Call Address
In MSP bus, the first 7-byte is the Slave address. Only the address match MSPADR the Slave will response an ACK_.
The exception is the general call address which can address all slave devices. When this address occur, all devices
should response an acknowledge.
The general call address is a special address which is reserved as all “0” of 7-bits address. The general call address
function is control by GCEN bit. Set this bit will enable general call address and clear it will disable. When GCEN=1,
following a START signal, 8-bit will shift into MSPSR and the address is compared with MSPADR and also the general
call address which fixed by hardware.
If the general call address matches, the MSPSR data is transferred into MSPBUF, the BF flag bit is set, and in the
falling edge of the ninth clock (ACK_) MSPIRQ flag set for interrupt request. In the interrupt service routine, reading
MSPBUF can check if the address is the general call address or device specific.
General Call Address Timing Diagram
13.6.5 Slave Wake up
When MCU enter Power down mode, if MSPENB bit is still set, MCU can wake-up by matched device address.
The address of MSP bus following START bit, 8-bits address will shift into MSPSR, if address matched, an NOT
Acknowledge will response on the ninth clock of SCL and MCU will be wake-up, MSPWK set and start wake-up
procedure but MSPIRQ will not set and MSPSR data will not load to MSPUBF. After MCU finish wake-up procedure,
MSP will be in idle status and waiting master’s START signal. Control register BF, MSPIRQ, MSPOV and MSPBUF will
be the same status/data before power down.
If address not matches, a NOT acknowledge is still sent on the ninth clock of SCL, but MCU will be NOT wake-up and
still keep in power down mode.
MSP Wake-up Timing Diagram: Address NOT Matched
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