
154
CHAPTER 6 INTERRUPTS
MB90560 series
6.7
Operation of the extended intelligent I/O service (EI2OS)
If an interrupt request is generated by a peripheral function, EI
2
OS activation is set in
the corresponding interrupt control register (ICR) that the CPU uses EI
2
OS to transfer
data. When the specified data transfer count terminates, the hardware interrupt is
automatically processed.
I
Operation flow of the extended intelligent I/O service (EI
2
OS)
Figure 6.7-1 shows the flow of EI
2
OS operation based on the internal microcode of the CPU.
Figure 6.7-1 Flow of extended intelligent I/O service (EI
2
OS) operation
Interrupt request generated
by peripheral function
Read ISD/ISCS
Termination
request from peripheral
function
IF = 0
BF = 0
DCT = 00
DIR = 1
ISE = 1
SE = 1
Data indicated by IOA
(data transfer)
memory indicated by BAP
Decrement DCT
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
(-1)
YES
Updage value
by BW
Updage value
by BW
YES
EI
2
OS termination processing
YES
Set S1 and S0 to 00
Set S1 and S0 to 01
Clear ISE to 0
Interrupt sequence
Clear interrupt request from
the peripheral function
Return to CPU operation
Set S1 and S0 to 11
Interrupt sequence
Data indicated by BAP
(data transfer)
memory indicated by BAP
Update IOA
Update BAP
ISD:
ISCS:
IF:
BW:
BF:
DIR:
SE:
EI2OS descriptor
EI2OS status register
IOA update/fixed selection bit in the EI2OS status register (ISCS)
Transfer data length specification bit in the EI2OS status register (ISCS)
BAP update/fixed selection bit in the EI2OS status register (ISCS)
Data transfer direction specification bit in the EI2OS status register (ISCS)
EI2OS termination control bit in the EI2OS status register (ISCS)
DCT:
IOA:
BAP:
ISE:
Data counter
I/O register address pointer
Buffer address pointer
EI2OS enable bit in the interrupt control
register
S1, S0: EI2OS status in the interrupt control
register (ICR)