SA-1100 Developer’s Manual 11-189
Peripheral Control Module
11.13.5 PPC Pin Assignment Register
The UART in serial port 1 and the SSP in serial port 4 can be reassigned to GPIO pins using the
PPC pin assignment register (PPAR). The PPAR contains two bits that control the reassignment of
each serial engine to an individual set of GPIO pins.

11.13.5.1 UART Pin Reassignment (UPR)

The UART pin reassignment (UPR) bit is used to select whether serial port 1’s UART is assigned
to GPIO pins 14 and 15. When UPR=0, serial port 1 uses its TXD1 and RXD1 pins, and the
SDLC/UART select (SUS) bit is used to select which protocol is enabled. When UPR=1, SUS is
ignored, serial port 1 defaults to SDLC operation using the TXD1 and RXD1 pins, and the UART
is configured to use GPIO<14> for transmit and GPIO<15> for receive. Note that the user must set
bits 14 and 15 in the GPIO alternate function register (GAFR) as well as set bit 14 and clear bit 15
in the GPIO pin direction register (GPDR). See the Section9.1, “General-Purpose I/O” on
page9-1.

11.13.5.2 SSP Pin Reassignment (SPR)

The SSP pin reassignment (SPR) bit is used to select whether serial port 4’s SSP is assigned to GPIO pins
10 through 13. When SPR=0, serial port 4 uses its TXD4, RXD4, SCLK, and SFRM pins; the MCP
enable (MCE) and SSP enable (SSE) bits are used to select which protocol is enabled (MCE has
precedence over SSE). When SPR=1, MCE and SSE must both be set; serial port 4 defaults to MCP
operation using the TXD4, RXD4, SCLK, and SFRM pins, and the SSP is configured to use GPIO<10>
for transmit, GPIO<11> for receive, GPIO<12> for serial clock, and GPIO<13> for serial frame. Note
that the user must set bits 10 through 13 in the GPIO alternate function register (GAFR) as well as set bits
10, 12, and 13 and clear bit 11 in the GPIO pin direction register (GPDR). See the Section9.1,
“General-Purpose I/O” on page9-1.
The following table shows the location of the two pin reassignment bits. Note that for reserved bits,
writes are ignored and reads return zero. Both control bits are cleared to zero following a reset of
the SA-1100, giving control of all GPIO pins to the system control module.
Address: 0h 9006 0008 PPAR: PPC Pin Assignment Register Read/Write
Bit 31302928272625242322212019181716
Reserved SPR Reserved
Reset0000000000000000
Bit1514131211109876543210
Reserved UPR Reserved
Reset0000000000000000
Bit Name Description
11..0 —Reserved.
12 UPR UA RT pin reassignment.
0 – No pin reassignment made, GPIO<14-15> controlled by GPIO unit, serial port 1
UART assigned to TXD1 and RXD1 if SUS=1.
1 – Pin reassignment made, serial port 1 defaults to SDLC operation (SUS ignored),
UART transmit assigned to GPIO<14> and receive to GPIO<15>, GAFR and GPDR
must be configured in GPIO unit.
17..13 — Reserved.
18 SPR SSP pin reassignment.
0 – No pin reassignment made, GPIO<10-13> controlled by GPIO unit, serial port 4
SSP assigned to TXD4, RXD4, SCLK, and SFRM if MCE=0 and SSE=1.
1– Pin reassignment made, serial port 4 defaults to MCP operation, SSP transmit
assigned to GPIO<10>, receive to GPIO<11>, serial clock to GPIO<12>, and serial
frame to GPIO<13>, GAFR and GPDR must be configured in GPIO unit.
31..19 — Reserved.