MEC1404 Datasheet, PDF (259/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
Note: The following notes apply:
- All examples assume that the SAEN configuration bit is 0.
- “Q” indicates the bit remains set at the previous state.
- *Not a standard sequence.
- **XX = Anything except D1.
- If multiple data bytes, set IBF and wait at state 0. Let the software know something unusual happened.
- For data bytes, only D[1] is used; all other bits are don't care.
- Host Commands (FF, FE, & D1) do not cause IBF. The method of blocking IBF in FIGURE 16-4: is the nIOW
not being asserted when FF, FE, & D1 Host commands are written”.
The hardware GATEA20 state machine returns to state S1 from state S2 when CMD = D1, as shown in the following
figures:.
FIGURE 16-3:
GATEA20 STATE MACHINE
RESET
CMD !=D1
or
DATA
[IBF=1]
S0
CMD = FF
[IBF=0]
CMD !=D1
or
CMD !=FF or
DATA
[IBF=1]
CMD !=D1
[IBF=1]
CMD = D1
S2
[IBF=0]
CMD = D1
[IBF=0]
CMD = D1
S1
[IBF=0]
Data
[IBF=0, Latch DIN
Notes: GateA20 Changes When in S1 going to S2
Clock = wrdinB
CMD = [C/D=1]
Data = [C/D=0]
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DS00001956D-page 259