Expanded Intelligent I/O Service Descriptor (Isd) - Fujitsu F2MC-16LX Hardware Manual

3.6.2

Expanded Intelligent I/O Service Descriptor (ISD)

The expanded intelligent I/O service descriptor is located in internal RAM between
000100 and 00017F
H
• Control data for data transfer
• Status data
• A buffer address pointer
■ Expanded Intelligent I/O Service Descriptor (ISD)
The expanded intelligent I/O service descriptor (ISD) is located in internal RAM between
000100
H
• Control data for data transfer
• Status data
• A buffer address pointer
Figure 3.6-3 shows the structure of the expanded intelligent I/O service descriptor.
Figure 3.6-3 Structure of the Expanded Intelligent I/O Service Descriptor
000100 + 8
H
ISD head address
■ Data Counter (DCT)
The DCT is a 16-bit register that functions as a counter of the number of transferred data
elements. This counter is decremented by one before the transfer of a data element. When this
counter becomes 0, the EI
. The descriptor contains:
H
and 00017F . The descriptor contains:
H
Eight high-order bits of the data counter (DCTH)
Eight low-order bits of the data counter (DCTL)
Eight high-order bits of the I/O address pointer (IOAH)
Eight low-order bits of the I/O address pointer (IOAL)
EI 2 OS status (ISCS)
Eight high-order bits of the buffer address pointer (BAPH)
Eight medium-order bits of the buffer address pointer (BAPM)
ICS
Eight low-order bits of the buffer address pointer (BAPL)
2
OS terminates.
3.6 Expanded Intelligent I/O Service (EI
2
OS)
H
L
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