UPSD3422_06 Datasheet, PDF (79/293 Pages) STMicroelectronics – Turbo Plus Series Fast Turbo 8032 MCU with USB and Programmable Logic

uPSD34xx
MCU bus interface
A[10:8] and the remaining pins can be configured for other functions such as generating
chip selects to the external devices.
Figure 20. Connecting external devices using ports A and B for address AD[15:0]
uPSD34xx
MCU
Module
AD[7:0]
AD[15:8]
PSEN
ALE
RD or WR
PSD
Module
Port B
Port A
A8-15
A0-7
D[7:0]
AI10434
RD or WR
External
8-bit
CS _Device
Figure 21. Connecting external devices using port A and an external latch for
address AD[15:0]
uPSD34xx
MCU
Module
AD[7:0]
AD[15:8]
PSEN
ALE
RD or WR
PSD
Module
A8-15
Port B
AI10435
D[7:0]
L
A
T
C
H
A7-0
RD or WR
External
8-bit
CS _Device
18.4
Programmable bus timing
The length of the bus cycles are user programmable at run time. The number of MCU_CLK
periods in a bus cycle can be specified in the SFR register named BUSCON (see Table 37
on page 81). By default, the BUSCON Register is loaded with long bus cycle times (6
MCU_CLK periods) after a reset condition. It is important that the post-reset initialization
firmware sets the bus cycle times appropriately to get the most performance, according to
Table 38 on page 82. Keep in mind that the PSD Module has a faster Turbo Mode (default)
and a slower but less power consuming Non-Turbo Mode. The bus cycle times must be
programmed in BUSCON to optimize for each mode as shown in Table 38. See
Section 28.5: PSD module detailed operation on page 201 for more details.
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