3.3 Interrupts
214
Chapter 3:Operation
s EI2OS status register (ISCS)
This 8-bit register indicates the update direction (increment/decrement) of the buffer address pointer
and the I/O register address pointer, the transfer data format (byte/word), the transfer direction, and
whether the buffer address pointer and the I/O register address pointer are updated or fixed. Fig. 3.3.10
shows the configuration of the ISCS register.
Fig. 3.3.10 ISCS Configuration
The contents of each bit are as follows:
[Bit 4] IF: This bit specifies whether the I/O register address pointer is updated or fixed.
0: The I/O register address pointer is updated after a data transfer.
1: The I/O register address pointer is not updated after a data transfer.
Note:
Only incrementing is possible.
[Bit 3] BW: This bit specifies the transfer data length.
0: Byte
1: Word
[Bit 2] BF: This bit specifies whether the buffer address pointer is updated or fixed.
0: The buffer address pointer is updated after a data transfer.
1: The buffer address pointer is not updated after a data transfer.
Note:
When updated, only the low-order 16 bits of the buffer address pointer are updated. Only
incrementing is possible.
[Bit 1] DIR:This bit specifies the data transfer length.
0: I/O
→ buffer
1: Buffer
→ I/O
[bit 0] SE: This bit controls the termination of the extended intelligent I/O service upon a request
from a resource.
0: The EI2OS does not terminate upon a request from a resource.
1: The EI2OS does terminate upon a request from a resource.
s Buffer address pointer (BAP)
This 24-bit register holds the address to be used next by the EI2OS for transfers. Because there is an
independent BAP for each EI2OS channel, each EI2OS channel can transfer data to an 16MB area. If
updating is specified by the BF bit in the ISCS, only the low-order 16 bits of the buffer address pointer
are updated. BAPH does not change.
Fig. 3.3.11 shows the operational flow of the EI2OS, while Fig. 3.3.12 shows the procedural flow for
using the EI2OS.
[CAUTION]
The MB90660A series operates only in single-chip mode, and therefore transfer is
enabled only to internal peripheral resources and internal RAM.
:ISCS (Indeterminate at reset)
Reserved ReservedReserved
IF
BW
BF
DIR
SE
7
6
5
4
3
2
1
0
* The write value to bits 7 to 5 of the ISCS register must always be ‘0.’