PIC18F2455_07 Datasheet, PDF (190/430 Pages) Microchip Technology – 28/40/44-Pin, High Performance, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

PIC18F2455/2550/4455/4550
REGISTER 18-2: SPPCFG: SPP CONFIGURATION REGISTER
R/W-0
CLKCFG1
bit 7
R/W-0
CLKCFG0
R/W-0
CSEN
R/W-0
CLK1EN
R/W-0
WS3
R/W-0
WS2
R/W-0
WS1
R/W-0
WS0
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 7-6
bit 5
bit 4
bit 3-0
CLKCFG1:CLKCFG0: SPP Clock Configuration bits
1x = CLK1 toggles on read or write of an Odd endpoint address;
CLK2 toggles on read or write of an Even endpoint address
01 = CLK1 toggles on write; CLK2 toggles on read
00 = CLK1 toggles only on endpoint address write; CLK2 toggles on data read or write
CSEN: SPP Chip Select Pin Enable bit
1 = RB4 pin is controlled by the SPP module and functions as SPP CS output
0 = RB4 functions as a digital I/O port
CLK1EN: SPP CLK1 Pin Enable bit
1 = RE0 pin is controlled by the SPP module and functions as SPP CLK1 output
0 = RE0 functions as a digital I/O port
WS3:WS0: SPP Wait States bits
1111 = 30 additional wait states
1110 = 28 additional wait states
•
•
•
•
0001 = 2 additional wait states
0000 = 0 additional wait states
18.1.2 CLOCKING DATA
The SPP has four control outputs:
• Two separate clock outputs (CK1SPP and
CK2SPP)
• Output enable (OESPP)
• Chip select (CSSPP)
Together, they allow for several different configurations
for controlling the flow of data to slave devices. When
all control outputs are used, the three main options are:
• CLK1 clocks endpoint address information while
CLK2 clocks data
• CLK1 clocks write operations while CLK2 clocks
reads
• CLK1 clocks Odd address data while CLK2 clocks
Even address data
Additional control options are derived by disabling the
CK1SPP and CSSPP outputs. These are enabled or
disabled with the CLK1EN and CSEN bits, respectively,
located in Register 18-2.
18.1.3 WAIT STATES
The SPP is designed with the capability of adding wait
states to read and write operations. This allows access
to parallel devices that require extra time for access.
Wait state clocking is based on the data source clock.
If the SPP is configured to operate as a USB endpoint,
then wait states are based on the USB clock. Likewise,
if the SPP is configured to operate from the micro-
controller, then wait states are based on the instruction
rate (FOSC/4).
The WS3:WS0 bits set the wait states used by the SPP,
with a range of no wait states to 30 wait states, in multi-
ples of two. The wait states are added symmetrically to
all transactions, with one-half added following each of the
two clock cycles normally required for the transaction.
Figure 18-3 and Figure 18-4 show signalling examples
with 4 wait states added to each transaction.
18.1.4 SPP PULL-UPS
The SPP data lines (SPP<7:0>) are equipped with
internal pull-ups for applications that may leave the port
in a high-impedance condition. The pull-ups are
enabled using the control bit, RDPU (PORTE<7>).
DS39632D-page 188
Preliminary
© 2007 Microchip Technology Inc.