USB2227/USB2228
DS00002256A-page 12 2007-2016 Microchip Technology Inc.
MA[1:0]/CLK_SE
L[1:0]
117
116
I/O8PD Memory Address Bus:
MA[1:0], These signals address memory locations within the
external memory.
SEL[1:0]. During nRESET assertion, these pins will select the
operating frequency of the external clock, and the corresponding
weak pull-down resistors are enabled. When nRESET is negated,
the value on these pins will be internal latched and these pins will
revert to MA[1:0] functionality, the internal pull-downs will be
disabled.
SEL[1:0] = ‘00’. 24MHz
SEL[1:0] = ‘01’. RESERVED
SEL[1:0] = ‘10’. RESERVED
SEL[1:0] = ‘11’. 48MHz
Note: If the latched value is ‘1’, then the corresponding MA
pin is tri-stated when the following conditions are true:
1. IDLE bit (PCON.0) is 1.
2. INT2 is negated
3. SLEEP bit of CLOCK_SEL is 1.
If the latched value is ‘0’, then the corresponding MA pin will
function identically to the MA[15:3] pins at all times (other than
during nRESET assertion).
nMWR 14 O8 Memory Write Strobe:
Program Memory Write; active low
nMRD 13 O8 Memory Read Strobe:
Program Memory Read; active low
nMCE 17 O8 Memory Chip Enable:
Program Memory Chip Enable; active low.
This signal is asserted, when any of the following conditions are
no longer met:
1. IDLE bit (PCON.0) is 1.
2. INT2 is negated
3. SLEEP bit of CLOCK_SEL is 1.
Note: This signal is held to a logic ‘high’ while nRESET is
asserted.
MISC
GPIO1 114 I/O8 General Purpose I/O:
This pin may be used either as input, edge sensitive interrupt
input, or output.
GPIO2 113 I/O8 General Purpose I/O:
This pin may be used either as input, edge sensitive interrupt
input, or output.
GPIO3 94 I/O8 General Purpose I/O:
This pin may be used either as input, edge sensitive interrupt
input, or output.
GPIO4 111 I/O8 General Purpose I/O:
This pin may be used either as input, edge sensitive interrupt
input, or output.
Symbol
128-Pin
VTQFP
Buffer Type Description
