2004 Mar 16
93
Philips Semiconductors
Product specification
PC-CODEC
SAA7108E; SAA7109E
10.3
Clock and real-time synchronization signals
A crystal accurate frequency reference is required for the
generation of the line-locked video (pixel) clock LLC, and
the frame-locked audio serial bit clock. An oscillator is
built-in, for fundamental or 3rd-harmonic crystals. The
supported crystal frequencies are 32.11 or 24.576 MHz
(defined during reset by strapping pin ALRCLK).
Alternatively pins XTALId and XTALIe can be driven from
an external single-ended oscillator.
The crystal oscillation can be propagated as clock to other
ICs in the system via pin XTOUTd.
The Line-Locked Clock (LLC) is the double pixel clock at a
nominal 27 MHz. It is locked to the selected video input,
generating baseband video pixels according to “ITU
recommendation 601” In order to support interfacing
circuits, a direct pixel clock LLC2 is also provided.
The pins for line and field timing reference signals are
RTCO, RTS1 and RTS0. Various real-time status
information can be selected for the RTS pins. The signals
are always available (output) and reflect the
synchronization operation of the decoder part in the
SAA7108E; SAA7109E. The function of the RTS1 and
RTS0pinscanbedefinedbybitsRTSE1[3:0]12H[7:4]and
RTSE0[3:0] 12H[3:0]; see Table 56.
Table 56
Clock and real-time synchronization signals
SYMBOL
PIN
I/O
DESCRIPTION
BIT
Crystal oscillator
XTALId
XTALOd
XTOUTd
P2
P3
P4
I
input for crystal oscillator, or reference clock
output of crystal oscillator
reference (crystal) clock output drive (optional)
XTOUTE[14H[3]]
O
O
Real-time signals (RT port)
LLC
M14
O
line-locked clock; nominal 27 MHz, double pixel clock locked to the
selected video input signal
line-locked pixel clock; nominal 13.5 MHz
real-time control output; transfers real-time status information
supporting RTC level 3.1 (see external document “RTC Functional
Description” available on request)
real-time status information line 0; can be programmed to carry
various real-time informations; see Table 167
real-time status information line 1; can be programmed to carry
various real-time informations; see Table 168
LLC2
RTCO
L14
L13
O
O
RTS0
K13
O
RTSE0[3:0] 12H[3:0]
RTS1
L10
O
RTSE1[3:0] 12H[7:4]