TPU 3035, TPU 3040
2. Functional Description
2.1. Conceptional Overview
The basic idea behind the TPU 3040 concept is the re-
placement of random logic by software. The still existing
hardware supports the on-chip CPU in tasks with high
data rates and ineffective software solutions. Typical
tasks of a teletext decoder are listed below (realization
on TPU 3040 in brackets):
– teletext data acquisition
– teletext data decoding
– page generation
– page memory management
– page display
– user interface
(hardware)
(software)
(software)
(software)
(hardware)
(software)
PRELIMINARY DATA SHEET
cessing this scratch buffer, the CPU stores reorganized
teletext lines into the page memory which takes up the
greatest space in the DRAM capacity. A third part of the
DRAM holds WST level 2 display data, which are read
out by the WST layer. The CPU has to generate the dis-
play data by decoding teletext information from the page
memory.
Apart from the WST layer, there is also one additional
on-chip OSD layer. The OSD layer accesses the on-chip
memory to read text and character font information. The
RGB outputs of the OSD layer can have higher priority
than the WST layer outputs. Thus it is possible to overlay
the teletext display with an additional layer for user guid-
ance.
The CPU memory contains RAM, program ROM and
character ROM. The character ROM holds the font data
and is separated from the program ROM to save CPU
time. The CPU can still access the character ROM via
a DMA interface including wait cycles. The WST layer
and the additional OSD layer can also access the CPU
memory via the same DMA interface.
The CPU is supported by some glue logic such as timer,
watchdog and interrupt controller and communicates
with the outside world via the I
2
C-Bus.
Fig. 2–1 shows the functional block diagram of the
TPU 3040. The software approach is realized using a
65C02 core with RAM and program ROM on chip. Via
I/O the CPU is connected to a DRAM interface. The
DRAM contains an acquisition scratch buffer which is
filled automatically by the teletext slicer circuit. After pro-
6
MICRONAS INTERMETALL
MICRONAS [ MICRONAS ]
