TC1796
Peripheral Units (Vol. 2 of 2)
Synchronous Serial Interface (SSC)
User’s Manual
20-11
V2.0, 2007-07
SSC, V2.1
1. If in Master Mode the Transmit Buffer register TB is loaded with new data for the
following transmission just at the end of the current transmission and a leading
delay > 0 is selected (SSOTC.LEAD not equal 00
B
), a slightly enlarged leading delay
(< one SCLK shift clock period) is generated for the following transmission.
20.1.2.5 Port Control
The SSC uses three lines to communicate with the external world. Pin SCLK serves as
the clock line, while pins MRST (Master Receive/Slave Transmit) and MTSR (Master
Transmit/Slave Receive) serve as the serial data input/output lines. As shown in
, these three lines (SCLK as input, Master Receive, Slave Receive) have two
inputs each at the SSC Module kernel. Three bits in register PISEL determine which of
the two kernel inputs (A or B) are connected. This feature allows for each of the three
SSC communication lines to be connected to two inputs coming from different port pins.
Operation of the SSC I/O lines depends on the selected operating mode (master or
slave). The direction of the port lines depends on the operating mode. The SSC will
automatically use the correct kernel output or kernel input line of the ports when
switching modes. Port pins assigned as SSC I/O lines can be controlled either by
hardware or by software.
When the SSC I/O lines are connected to dedicated pins, hardware I/O control should
typically be used. In this case, two output signals reflect the state of the CON.EN and
CON.MS bits directly (the M/S select line is inverted to the CON.MS bit definition).
When the SSC I/O lines are connected with bi-directional lines of general purpose I/O
ports, software I/O control should be typically used. In this case, port registers must be
programmed for alternate output and input selection. When switching between master
and slave mode, port registers must be reprogrammed.
Using the open-drain output feature of port lines helps to avoid bus contention problems
and reduces the need for hard-wired hand-shaking or slave select lines. In open-drain
output mode, it is not always necessary to switch the direction of a port pin. Note that in
hardware-controlled I/O mode, the availability of open-drain outputs depends on the type
of the dedicated output pins that are used. The SSC module itself does not provide any
control capability for open-drain control.
Note: For details of SSC port connections and configuration, see
.
