Cypress EZ-USB Series 2100 Service Manual download pdf (Page 119)

Page 6-22 Chapter 6. EZ-USB CPU EZ-USB TRM v1.9

Bulk endpoint data is available in 64-byte buffers in EZ-USB RAM. In some cases it is

preferable to access bulk data as a FIFO register rather than as a RAM. The EZ-USB core

provides a special data pointer which automatically increments when data is transferred.

Using this Autopointer, the 8051 can access any contiguous block of internal EZ-USB

RAMasaFIFO.

Figure 6-12. Autopointer Registers

The 8051 first loads AUTOPTRH and AUTOPTRL with a RAM address (for example the

address of a bulk endpoint buffer). Then, as the 8051 reads or writes data to the data reg-

ister AUTODATA, the address is supplied by AUTOPTRH/L, which automatically incre-

ments after every read or write to the AUTODATA register. The AUTOPTRH/L registers

may be written or read at anytime. These registers maintain the current pointer address, so

the 8051 can read them to determine where the next byte will be read or written.

6.16 The Autopointer

AUTOPTRH Autopointer Address High 7FE3

b7 b6 b5 b4 b3 b2 b1 b0

A15 A14 A13 A12 A11 A10 A9 A8

R/W R/W R/W R/W R/W R/W R/W R/W

x x x x x x x x

AUTOPTRL Autopointer Address Low 7FE4

b7 b6 b5 b4 b3 b2 b1 b0

A7 A6 A5 A4 A3 A2 A1 A0

R/W R/W R/W R/W R/W R/W R/W R/W

x x x x x x x x

AUTODATA Autopointer Data 7FE5

b7 b6 b5 b4 b3 b2 b1 b0

D7 D6 D5 D4 D3 D2 D1 D0

R/W R/W R/W R/W R/W R/W R/W R/W

x x x x x x x x

1 2 ... 114 115 116 117 118 119 120 121 122 123 124 ... 333 334

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Cypress EZ-USB Series 2100 Service Manual Page 119