saa5647hl NXP Semiconductors, saa5647hl Datasheet - Page 51

• Manufacturer Part Number: saa5647hl
• Description: Saa56xx Enhanced Tv Microcontrollers With On-screen Display Osd
• Manufacturer: NXP Semiconductors

Philips Semiconductors
21 MEMORY INTERFACE
The memory interface controls access to the embedded
DRAM, refreshing of the DRAM and page clearing. The
DRAM is shared between Data Capture, display and
microcontroller sections.
The Data Capture section uses the DRAM to store
acquired information that has been requested. The display
reads from the DRAM information and converts it to RGB
values. The microcontroller uses the DRAM as embedded
auxiliary RAM.
21.1
The memory is partitioned into two distinct areas, the
dedicated Auxiliary RAM area and the Display RAM area.
When not being used for Data Capture or display, the
Display RAM area can be used as an extension to the
auxiliary RAM area.
21.1.1
The Auxiliary RAM is not initialised at power-up and must
be initialised by the application software. Its contents are
maintained during Idle mode and Standby mode, but are
lost if Power-down mode is entered.
2004 Sep 03
Enhanced TV microcontrollers with
On-Screen Display (OSD)
Memory structure
A
UXILIARY
RAM
Fig.14 Additional glue logic required to address 256 kbytes of external ROM.
SAA56XX
A 15_BK
A 17_LN
ROMBK1
ROMBK0
51
21.1.2
The Display RAM is initialised on power-up to a value of
20H throughout. The contents of the Display RAM are
maintained when entering Idle mode. If Idle mode is exited
using an interrupt, the contents are unchanged, if Idle
mode is exited using an external reset, the contents are
initialised to 20H.
Full Closed Caption display requires display RAM from
8000H to 845FH. The memory from 8460H to 84FFH
(must be initialised by the application software) can be
utilised as an extension to the dedicated contiguous
Auxiliary RAM that occupies 0000H to 07FFH.
21.2
The dedicated auxiliary RAM area occupies 2 kbytes, with
an address range from 0000H to 07FFH. The Display
RAM occupies a maximum of 12 kbytes with an address
range from 2000H to 5000H for TXT mode and
8000H to 84FFH for CC mode (see Fig.15). Although
having different address ranges, the two modes occupy
physically the same DRAM area.
Memory mapping
D
ISPLAY
RAM
A17
A16
A15
ROM
mgu488
Product specification
SAA56xx