![](http://datasheet.mmic.net.cn/330000/MB90F553A_datasheet_16437927/MB90F553A_8.png)
MB90550A/550B Series
8
(Continued)
Pin no.
Pin name
Circuit type
Function
QFP
LQFP
14
12
P34
E
(CMOS)
General-purpose I/O port.
This function is enabled in single-chip mode
HRQ
Hold request input pin.
This function is enabled in an external-bus enabled mode.
15
13
P35
E
(CMOS)
General-purpose I/O port.
This function is enabled in single-chip mode.
HAK
Hold acknowledge output pin.
This function is enabled in an external-bus enabled mode.
16
14
P36
E
(CMOS)
General-purpose I/O port.
This function is enabled in single-chip mode.
RDY
Ready signal input pin.
This function is enabled in an external-bus enabled mode.
17
15
P37
E
(CMOS)
General-purpose I/O port.
This function is enabled in single-chip mode.
CLK
CLK output pin.
This function is enabled in an external-bus enabled mode.
18
16
P40
F
(CMOS/H)
General-purpose I/O port.
Serves as an open-drain output port (OD40 = 1) depending on the
setting of the open-drain control setting register (ODR4).
(D40 = 0: Disabled when the port is set for input.)
SCK
UART serial clock I/O pin.
This function is enabled with the UART clock output enabled.
19
17
P41
F
(CMOS/H)
General-purpose I/O port.
Serves as an open-drain output port (OD41 = 1) depending on the
setting of the open-drain control setting register (ODR4).
(D41 = 0: Disabled when the port is set for input.)
SOT
UART serial data output pin.
This function is enabled with the UART serial data output enabled.
20
18
P42
F
(CMOS/H)
General-purpose I/O port.
Serves as an open-drain output port (OD42 = 1) depending on the
setting of the open-drain control setting register (ODR4).
(D42 = 0: Disabled when the port is set for input.)
SIN
UART serial data input pin. Since this input is used as required while
the UART is operating for input, the output by any other function
must be off unless used intentionally.
21
19
P43
F
(CMOS/H)
General-purpose I/O port.
Serves as an open-drain output port (OD43 = 1) depending on the
setting of the open-drain control setting register (ODR4).
(D43 = 0: Disabled when the port is set for input.)
SCK1
Extended I/O serial clock I/O pin. This function is enabled with the
extended I/O serial clock output enabled.