SAA5531 Philips Semiconductors, SAA5531 Datasheet - Page 33

• Manufacturer Part Number: SAA5531
• Description: Enhanced TV microcontrollers with On-Screen Display OSD
• Manufacturer: Philips Semiconductors

Philips Semiconductors
10.3
This mode is only available on 1 page devices. When
Standby mode is entered both Acquisition and Display
sections are disabled. The following functions remain
active:
To enter Standby mode, the STANDBY control bit in the
ROMBANK SFR (bit 7) must be set. It can be used in
conjunction with either Idle or Power-down modes to
switch between power saving modes. This mode enables
the 80C51 core to decode either IR remote commands or
receive I
powered.
The Standby state is maintained upon exit from either the
Idle mode or Power-down mode. No wake-up from
Standby is necessary as the 80C51 core remains
operational.
Since the output values on RGB and VDS are maintained
the display output must be disabled before entering this
mode.
11 I/O FACILITY
11.1
The SAA55xx devices have 29 I/O lines, each is
individually addressable, or form 3 parallel 8-bit
addressable ports which are Port 0, Port 1 and Port 2.
Port 3 has 5-bit parallel I/O only.
11.2
All individual ports can be programmed to function in one
of four I/O configurations: open-drain, quasi-bidirectional,
high-impedance and push-pull. The I/O configuration is
selected using two associated Port Configuration
Registers: PnCFGA and PnCFGB (where n = port number
0, 1, 2 or 3); see Table 5.
2000 Feb 23
80C51 core
Memory interface
I
Timer/Counters
Watchdog Timer
Software ADC
Pulse Width Modulators
Enhanced TV microcontrollers with
On-Screen Display (OSD)
2
C-bus interface
Standby mode
I/O ports
Port type
2
C-bus commands without the device being fully
33
11.2.1
The open-drain configuration can be used for bidirectional
operation of a port. It requires an external pull-up resistor,
the pull-up voltage has a maximum value of 5.5 V, to allow
connection of the device into a 5 V environment.
The I
configured as open-drain.
11.2.2
The quasi-bidirectional configuration is a combination of
open-drain and push-pull. It requires an external pull-up
resistor to V
from LOW-to-HIGH is output from the device, the pad is
put into push-pull configuration for one clock cycle
(166 ns) after which the pad goes into open-drain
configuration. This configuration is used to speed up the
edges of signal transitions. This is the default mode of
operation of the pads after reset.
11.2.3
The high-impedance configuration can be used for input
only operation of the port. When using this configuration
the two output transistors are turned off.
11.2.4
The push-pull configuration can be used for output only.
In this mode the signal is driven to either 0 V or V
which is nominally 3.3 V.
11.3
Ports 1, 2 and 3 are shared with alternative functions to
enable control of external devices and circuitry.
The alternative functions are enabled by setting the
appropriate SFR and also writing a logic 1 to the port bit
that the function occupies.
11.4
Port pins P0.5 and P0.6 have a 8 mA current sinking
capability to enable LEDs in series with current limiting
resistors to be driven directly, without the need for
additional buffering circuitry.
2
C-bus ports (P1.4, P1.5, P1.6 and P1.7) can only be
Port alternative functions
LED support
O
Q
H
P
USH
IGH
PEN
UASI
DDP
-
-
-
IMPEDANCE
-
PULL
DRAIN
BIDIRECTIONAL
(normally 3.3 V). When a signal transition
Preliminary specification
SAA55xx
DDP
,