Oki MSM66591, User Manual

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MSM66591/ML66592 User's Manual
Chapter 22 Expansion Port
22. Expansion Port
The MSM66591/ML66592 have a 1-channel internal expansion port for the external
expansion of general-purpose ports.
The expansion port expands port functions by outputting parallel data of the internal
registers as synchronous serial data, and by externally converting serial data to parallel
data.
External parallel data can also be input as synchronous serial data and converted to
parallel data internally. Data input and output uses pin P10_6/SFTDAT, the shift clock
output uses pin P10_5/SFTCLK, and the external latch strobe uses pin P10_7/SFTSTB.
The data length is selectable as 8 bits or 16 bits. Connection of devices such as a
74HC165 is assumed for external input and a 74HC595 is assumed for external output
of the expansion port. Because expansion port functions are assigned as secondary
functions of Port 10, corresponding bits of the Port 10 secondary function control
register must be set to "1" to use expansion port functions.
22.1 Expansion Port Configuration
The expansion port consists of a 16-bit shift register that exchanges data with the
exterior, a 16-bit buffer register (EXTPD) for the shift register, EXTPCON to control
operation, and a control circuit.
Figure 22-1 shows the configuration of the expansion port.
Figure 22-1 Expansion Port Configuration
Internal BUS
Shift Register
Control Circuit
EXTPD
EXTPCON
1/4 CLK
P10_6/SFTDAT
P10_5/SFTCLK
P10_7/SFTSTB