Ei 2 Os Status Register (Iscs) - Fujitsu MB90390 Series Hardware Manual

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3.7.2 EI OS Status Register (ISCS)
This 8-bit register indicates the update direction (increment/decrement), transfer data
format (byte/word), and transfer direction of the buffer address pointer and the I/O
register address pointer. This register also indicates whether the buffer address pointer
or I/O register address pointer is updated or fixed.
2
■ EI
OS Status Register (ISCS)
Figure 3.7-5 is a diagram of the ISCS configuration.
bit 7 6
Reserved Reserved
Note: Always write "0" to bit7 to bit5 of ISCS.
Each bit is described below.
[bit4] IF: Specify whether the I/O register address pointer is updated or fixed.
0: The I/O register address pointer is updated after data transfer.
1: The I/O register address pointer is not updated after data transfer.
Note:
Only increment is allowed.
[bit3] BW: Specify the transfer data length.
0: Byte
1: Word
[bit2] BF: Specify whether the buffer address pointer is updated or fixed.
0: The buffer address pointer is updated after data transfer.
1: The buffer address pointer is not updated after data transfer.
Note:
Only the low-order 16 bits of the buffer address are updated. Only increment is allowed.
[bit1] DIR: Specify the data transfer direction.
0: I/O address pointer → Buffer address pointer
1: Buffer address pointer → I/O address pointer
Figure 3.7-5 ISCS Configuration
5 4 3
Reserved IF BW
2 1 0
BF DIR SE
CHAPTER 3 INTERRUPTS
ISCS
(Undefined when reset)
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