PI7C8150B_15 Datasheet, PDF (68/107 Pages) Pericom Semiconductor Corporation – ASYNCHRONOUS 2-PORT PCI-TO-PCI BRIDGE

PI7C8150B
ASYNCHRONOUS 2-PORT PCI-TO-PCI BRIDGE
 Write-1-to-clear signal output enable control field
 Input data field
The bottom four bits of the output enable fields control whether each GPIO signal is input
only or bi-directional. Each signal is controlled independently by a bit in each output
enable control field. If a 1 is written to the write-1-to-set field, the corresponding pin is
activated as an output. If a 1 is written to the write-1-to-clear field, the output driver is tri-
stated, and the pin is then input only. Writing zeroes to these registers has no effect. The
reset for these signals is input only.
The input data field is read only and reflects the current value of the GPIO pins. A type 0
configuration read operation to this address is used to obtain the values of these pins. All
pins can be read at any time, whether configured as input only or as bi-directional.
The output data fields also use the write-1-to-set and write-1-to-clear mode. If a 1 is
written to the write-1-to-set field and the pin is enabled as an output, the corresponding
GPIO output is driven HIGH. If a 1 is written to the write-1-to-clear field and the pin is
enabled as an output, the corresponding GPIO output is driven LOW. Writing zeros to
these registers has no effect. The value written to the output register will be driven only
when the GPIO signal is configured as bi-directional. A type 0 configuration write
operation is used to program these fields. The rest value for the output is 0.
10.2
SECONDARY CLOCK CONTROL
The PI7C8150B uses the GPIO pins and the MSK_IN signal to input a 16-bit serial data
stream. This data stream is shifted into the secondary clock control register and is used for
selectively disabling secondary clock outputs.
The serial data stream is shifted in as soon as P_RST_L is detected deasserted and the
secondary reset signal, S_RST_L, is detected asserted. The deassertion of S_RST_L is
delayed until the PI7C8150B completes shifting in the clock mask data, which takes 23
clock cycles. After that, the GPIO pins can be used as general-purpose I/O pins.
An external shift register should be used to load and shift the data. The GPIO pins are used
for shift register control and serial data input. Table 10-1 shows the operation of the GPIO
pins.
Table 10-1. GPIO Operation
GPIO[0]
GPIO[1]
GPIO[2]
GPIO Pin
GPIO[3]
Operation
Shift register clock output at 33MHz max frequency
Not used
Shift register control
0: Load
1: Shift
Not used
The data is input through the dedicated input signal, MSK_IN.
The shift register circuitry is not necessary for correct operation of PI7C8150B. The shift
register can be eliminated, and MSK_IN can be tied LOW to enable all secondary clock
outputs or tied HIGH to force all secondary clock outputs HIGH. Table 10-2 shows the
format of the serial stream.
15-0048
Page 68 of 107
April 2015 – Revision 2.1