Cypress Semiconductor FX2LP Informações Técnicas Página 262

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EZ-USB FX2 Technical Reference Manual
Page 11-8 EZ-USB FX2 Technical Reference Manual v2.1
All other on-chip FX2 RAM (program/data memory, endpoint buffer memory, and the FX2 control
registers) is addressed as though it were
off-chip
8051 memory. FX2 firmware reads or writes
these bytes as data using the MOVX (“move external”) instruction, even though the FX2 RAM and
register set is actually inside the EZ-USB FX2 chip. Off-chip memory attached to the FX2 address
and data buses (CY7C68013-128NC only) can also be accessed by the MOVX instruction. FX2
logic encodes its memory strobe and select signals (RD
, WR, CS, OE, and PSEN) to eliminate the
need for external logic to separate the on-chip and off-chip memory spaces; see Chapter 5, "Mem-
ory".
11.9 I/O Ports
The FX2 implements I/O ports differently than a standard 8051, as described in Chapter 13,
"Input/Output".
The FX2 has up to five 8-bit wide, bidirectional I/O ports. Each port is associated with a pair of reg-
isters:
An “OEx” register, which sets the input/output direction of each of the 8 port pins
(0 = input, 1 = output).
An “IOx” register. Values written to IOx appear on the pins configured as outputs; values
read from IOx indicate the states of the 8 pins, regardless of input/output configuration.
Most I/O pins have alternate functions which are selected using configuration registers. When an
alternate configuration is selected for an I/O pin, the corresponding OEx bit is ignored (see
Section
13.2
). The default (power-on reset) state of all I/O ports is: alternate configurations
off
, all I/O pins
configured as inputs.
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