7641 datasheet(80/385 Pages) RENESAS

80 / 385 page

Rev.2.00

Aug 28, 2006

page 63 of 113

7641 Group

REJ09B0336-0200

HARDWARE

FUNCTIONAL DESCRIPTION

[Data Bus Buffer Status Register 0, 1 (DBBS0, DBBS1)]

004916, 004D16

The data bus buffer status registers 0, 1 consist of eight bits each.

Bits 0, 1, and 3 are read-only bits and indicate the status of the

data bus buffer. Bits 2, 4, 5, 6, and 7 are user definable flags

which can be programed, and can be read/written. The host CPU

can only read this register when the A0 pin is set to “H”.

•Bit 0: Output buffer full flag OBF0, OBF1

When writing data to the output data bus buffer, this flag is set to

“1”. When reading the output data bus buffer from the host CPU,

this flag is cleared to “0”.

•Bit 1: Input buffer full flag IBF0, IBF1

When writing data from the host CPU to the input data bus

buffer, this flag is set to “1”. When reading the input data bus

buffer from the slave CPU side, this flag is are cleared to “0”.

•Bit 3: A0 flag A00, A01

When writing data from the host CPU to the input data bus

buffer, the level of the A0 pin is latched.

[Input Data Bus Buffer Registers 0, 1 (DBBIN0, DBBIN1)]

004816, 004C16

Data on the data bus is latched to DBBIN0 or DBBIN1 by writing

request from the host CPU. Data of DBBINs can be read from the

Data Bus Buffer Registers (address 004816 or 004C16) on the

SFR area.

[Output Data Bus Buffer Registers 0, 1 (DBBOUT 0,

DBBOUT1)] 004816, 004C16

When writing data to the Data Bus Buffer Registers (address

004816 or 004C16) on the SFR area, data is set to DBBOUT0 or

DBBOUT1. Data of DBBOUTs is output onto the data bus by per-

forming the reading request from the host CPU when the A0 pin is

set to “L”.

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