Intermec 074787-001 User Manual
Chapter 2 — Theory of Operation
PB42 Portable Receipt Printer Service Manual
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Secondary Serial Test Port Communication Lines
The SMC UART has no flow control. So, it has only RX and TX. The
SMC TX signal is connected directly to the test port. For the SMC RX
signal, a 2:1 mux (U15) is used to switch between the PCTXD and the test
port TX signal. To operate properly, the DETECT pin (pin 4) of the test
cable must be grounded. When DETECT is grounded, the mux selects the
test port. When DETECT is left floating, the mux selects PCTXD.
SMC TX signal is connected directly to the test port. For the SMC RX
signal, a 2:1 mux (U15) is used to switch between the PCTXD and the test
port TX signal. To operate properly, the DETECT pin (pin 4) of the test
cable must be grounded. When DETECT is grounded, the mux selects the
test port. When DETECT is left floating, the mux selects PCTXD.
User Interface
The user interface consists of 2 buttons, 7 LEDs, and a speaker for audible
alerts. The following sections describe how these have been implemented in
hardware and how to control them in software.
alerts. The following sections describe how these have been implemented in
hardware and how to control them in software.
Speaker Driver
send data to the DAC.
Before streaming data to the DAC, the amplifier must be enabled. This is
accomplished by setting SPKR_EN (PD8) to output high. To conserve
power, SPKR_EN must be set to output low when not alerting.
accomplished by setting SPKR_EN (PD8) to output high. To conserve
power, SPKR_EN must be set to output low when not alerting.