USBN9604 National Semiconductor, USBN9604 Datasheet - Page 14

• Manufacturer Part Number: USBN9604
• Description: USBN9603/USBN9604 Universal Serial Bus Full Speed Node Controller with Enhanced DMA Support
• Manufacturer: National Semiconductor

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3.0 Parallel Interface
3.1.1
The standard access sequence for non-multiplexed mode is to write the address to the ADDR register and then read or write
the data from/to the DATA_OUT/DATA_IN register. The DATA_OUT register is updated after writing to the ADDR register.
The ADDR register or the DATA_OUT/DATA_IN register is selected with the A0 input.
3.1.2
In burst mode, the ADDR register is written once with the desired memory address of any of the on-chip registers. Then
consecutive reads/writes are performed to the DATA_IN/DATA_OUT register without previously writing a new address. The
content of the DATA_OUT register for read operations is updated once after every read or write.
3.1.3
The following table gives an overview of the parallel interface registers in non-multiplexed mode.
The reserved bits return undefined data on read and should be written with 0.
Address Register (ADDR)
The ADDR register acts as a pointer to the internal memory. This register is write only and is cleared on reset.
Data Output Register (DATA_OUT)
The DATA_OUT register is updated with the contents of the memory register to which the ADDR register is pointing. Update
occurs under the following conditions:
1. After the ADDR register is written.
2. After a read from the DATA_OUT register.
3. After a write to the DATA_IN register.
This register is read only and holds undefined data after reset.
Data Input Register (DATA_IN)
The DATA_IN register holds the data written to the device address to which ADDR points. This register is write only and is
cleared on reset.
Standard Access Mode
Burst Mode
User Registers
A0
0
0
1
1
Access
Read
Write
Read
Write
(Continued)
bit 7
Reserved
bit 6
bit 5
14
bit 4
DATA_OUT
Reserved
DATA_IN
bit 3
ADDR5-0
bit 2
bit 1
bit 0