Table 1-3. EZ-USB Series 2100 Pinouts by Pin Function
2125S
2126S
2135S
2136S
2121S
2131Q 2122S
2131S
2122T 2126T
Name
Type Default
Description
71
73
74
75
N/A
N/A
N/A
N/A
N/A
44
N/A PA3 or CS#
I/O
I
Multiplexed pin whose function is selected by the CS
(PA3) bit of the PORTACFG register. If CS=0, the pin is
the bi-directional I/O port pin PA3. If CS=1, the pin is
an active-low chip select for external memory. If the
CS# pin is used, it should be externally pulled up to
Vcc to ensure that the write strobe is inactive (high)
at power-on.
39
39
N/A PA4 or FWR# I/O
I
Multiplexed pin whose function is selected by the
(PA4) FWR (Fast Write) bit of the PORTAFCG register. If
FWR=0, the pin is the bi-directional I/O port pin PA4.
If FWR=1, the pin is the write strobe for an external
FIFO. If the FWR# pin is used, it should be exter-
nally pulled up to Vcc to ensure that the write strobe
is inactive (high) at power-on.
40
40
N/A PA5 or FRD# I/O
I
Multiplexed pin whose function is selected by the
(PA5) FRD (Fast Read) bit of the PORTAFCG register. If
FRD=0, the pin is the bi-directional I/O port pin PA5.
If FRD=1, the pin is the read strobe for an external
FIFO. If the FRD# pin is used, it should be exter-
nally pulled up to Vcc to ensure that the write strobe
is inactive (high) at power-on.
N/A
N/A
44
PA6 or
I/O
I
Multiplexed pin whose function is selected by the
RXD0OUT
(PA6) RXD0OUT bit of the PORTAFCG register. If
RXD0OUT=0 (default), the pin is the bi-directional
I/O port bit PA6. If RXD0OUT=1, the pin is the
active-high RXD0OUT signal from 8051 UART0.
If RXD0OUT is selected and UART0 is in mode 0,
this pin provides the output data for UART0 only
when it is in sync mode. Otherwise, it is a 1.
76
N/A
N/A
8
8
PA7 OR
I/O
I
Multiplexed pin whose function is selected by the
RXD1OUT
(PA7) RXD1OUT bit of the PORTAFCG register. If
RXD1OUT=0 (default), the pin is the bi-directional
I/O port bit PA7. If RXD1OUT=1, the pin is the
active-high RXD1OUT signal from 8051 UART1.
When RXD1OUT is selected and UART1 is in mode
0, this pin provides the output data for UaRT1 only
when it is in sync mode. In modes 1, 2, and 3, this
pin is a 1.
EZ-USB TRM v1.9
Chapter 1. Introducing EZ-USB
Page 1-25
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