diff --git a/board/cr50/ap_uart_state.c b/board/cr50/ap_uart_state.c
index 42e2feeab4..c21e8b518c 100644
--- a/board/cr50/ap_uart_state.c
+++ b/board/cr50/ap_uart_state.c
@@ -21,6 +21,12 @@ void print_ap_uart_state(void)
 	ccprintf("AP UART: %s\n", device_state_name(state));
 }
 
+int ap_is_suspended(void)
+{
+	/* When the AP uart is off, that means the device is suspended. */
+	return state == DEVICE_STATE_OFF;
+}
+
 int ap_uart_is_on(void)
 {
 	/* Debouncing and on are both still on */
diff --git a/board/cr50/board.c b/board/cr50/board.c
index 3a3eaf6d5a..b01b3571a3 100644
--- a/board/cr50/board.c
+++ b/board/cr50/board.c
@@ -149,6 +149,11 @@ int board_rst_pullup_needed(void)
 	return !!(board_properties & BOARD_NEEDS_SYS_RST_PULL_UP);
 }
 
+int board_needs_s3_term(void)
+{
+	return !!(board_properties & BOARD_NEEDS_S3_TERM);
+}
+
 int board_tpm_uses_i2c(void)
 {
 	return !!(board_properties & BOARD_SLAVE_CONFIG_I2C);
diff --git a/board/cr50/board.h b/board/cr50/board.h
index c87cd3e651..75f25cc533 100644
--- a/board/cr50/board.h
+++ b/board/cr50/board.h
@@ -262,6 +262,9 @@ int board_tpm_uses_spi(void);
 int board_id_is_mismatched(void);
 /* Allow for deep sleep to be enabled on AP shutdown */
 int board_deep_sleep_allowed(void);
+int board_needs_s3_term(void);
+int board_s3_term_is_enabled(void);
+void board_s3_term(int enable);
 
 void power_button_record(void);
 
@@ -282,6 +285,7 @@ void print_servo_state(void);
 
 int ap_is_on(void);
 int ap_uart_is_on(void);
+int ap_is_suspended(void);
 int ec_is_on(void);
 int ec_is_rx_allowed(void);
 int servo_is_connected(void);
diff --git a/board/cr50/build.mk b/board/cr50/build.mk
index 049e29eafc..c245920bcd 100644
--- a/board/cr50/build.mk
+++ b/board/cr50/build.mk
@@ -39,6 +39,7 @@ board-${CONFIG_RDD} += rdd.o
 board-${CONFIG_USB_SPI} += usb_spi.o
 board-${CONFIG_USB_I2C} += usb_i2c.o
 board-y += recovery_button.o
+board-y += s3_term.o
 board-y += tpm2/NVMem.o
 board-y += tpm2/aes.o
 board-y += tpm2/ecc.o
diff --git a/board/cr50/rdd.c b/board/cr50/rdd.c
index d59ca7d803..15173ba70a 100644
--- a/board/cr50/rdd.c
+++ b/board/cr50/rdd.c
@@ -145,6 +145,9 @@ enum ccd_state_flag {
 
 	/* SPI port is enabled for AP and/or EC flash */
 	CCD_ENABLE_SPI			= (1 << 6),
+
+	/* S3 Terminations are enabled */
+	CCD_ENABLE_S3_TERM		= (1 << 7),
 };
 
 int console_is_restricted(void)
@@ -179,6 +182,9 @@ static uint32_t get_state_flags(void)
 	if (ccd_usb_spi.state->enabled_device)
 		flags_now |= CCD_ENABLE_SPI;
 
+	if (board_s3_term_is_enabled())
+		flags_now |= CCD_ENABLE_S3_TERM;
+
 	return flags_now;
 }
 
@@ -204,6 +210,8 @@ static void print_state_flags(enum console_channel channel, uint32_t flags)
 		cprintf(channel, " I2C");
 	if (flags & CCD_ENABLE_SPI)
 		cprintf(channel, " SPI");
+	if (flags & CCD_ENABLE_S3_TERM)
+		cprintf(channel, " S3_TERM");
 }
 
 static void ccd_state_change_hook(void)
@@ -242,6 +250,10 @@ static void ccd_state_change_hook(void)
 				CCD_ENABLE_UART_EC_BITBANG | CCD_ENABLE_I2C |
 				CCD_ENABLE_SPI);
 
+	/* Enable S3 Terminations */
+	if (ap_is_suspended() && board_needs_s3_term())
+		flags_want |= CCD_ENABLE_S3_TERM;
+
 	/* Disable based on capabilities */
 	if (!ccd_is_cap_enabled(CCD_CAP_GSC_RX_AP_TX))
 		flags_want &= ~CCD_ENABLE_UART_AP;
@@ -305,6 +317,8 @@ static void ccd_state_change_hook(void)
 		usb_i2c_board_disable();
 	if (delta & CCD_ENABLE_SPI)
 		usb_spi_enable(&ccd_usb_spi, 0);
+	if (delta & CCD_ENABLE_S3_TERM)
+		board_s3_term(0);
 
 	/* Handle turning things on */
 	delta = flags_want & ~flags_now;
@@ -324,6 +338,8 @@ static void ccd_state_change_hook(void)
 		usb_i2c_board_enable();
 	if (delta & CCD_ENABLE_SPI)
 		usb_spi_enable(&ccd_usb_spi, 1);
+	if (delta & CCD_ENABLE_S3_TERM)
+		board_s3_term(1);
 }
 DECLARE_DEFERRED(ccd_state_change_hook);
 
diff --git a/board/cr50/s3_term.c b/board/cr50/s3_term.c
new file mode 100644
index 0000000000..bb486d207e
--- /dev/null
+++ b/board/cr50/s3_term.c
@@ -0,0 +1,88 @@
+/* Copyright 2018 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "console.h"
+#include "registers.h"
+
+#define CPRINTS(format, args...) cprints(CC_SYSTEM, format, ## args)
+#define CPRINTF(format, args...) cprintf(CC_SYSTEM, format, ## args)
+
+#define AP_TX_TERM	(1 << 0)
+#define SPS_TERM	(1 << 1)
+
+int term_enabled;
+
+static void update_term_state(int term, int enable)
+{
+	if (enable)
+		term_enabled |= term;
+	else
+		term_enabled &= ~term;
+}
+
+int board_s3_term_is_enabled(void)
+{
+	return term_enabled;
+}
+
+static void ap_tx_term_enable(int term_enable)
+{
+	/* Add a pulldown to AP TX Cr50 RX */
+	GWRITE_FIELD(PINMUX, DIOA3_CTL, PD, term_enable);
+	update_term_state(AP_TX_TERM, term_enable);
+}
+
+static void sps_enable_pd(int term_enable)
+{
+	GWRITE_FIELD(PINMUX, DIOA2_CTL, PD, term_enable);	/* SPS_MOSI */
+	GWRITE_FIELD(PINMUX, DIOA6_CTL, PD, term_enable);	/* SPS_CLK */
+	GWRITE_FIELD(PINMUX, DIOA10_CTL, PD, term_enable);	/* SPS_MISO */
+	GWRITE_FIELD(PINMUX, DIOA12_CTL, PD, term_enable);	/* SPS_CS_L */
+}
+
+static void sps_enable_inputs(int input_enable)
+{
+	GWRITE_FIELD(PINMUX, DIOA2_CTL, IE, input_enable);	/* SPS_MOSI */
+	GWRITE_FIELD(PINMUX, DIOA6_CTL, IE, input_enable);	/* SPS_CLK */
+	GWRITE_FIELD(PINMUX, DIOA10_CTL, IE, 0);		/* SPS_MISO */
+	GWRITE_FIELD(PINMUX, DIOA12_CTL, IE, input_enable);	/* SPS_CS_L */
+}
+
+static void sps_term_enable(int term_enable)
+{
+	/* Disable the sps inputs before enabling the pulldowns */
+	if (!term_enable)
+		sps_enable_inputs(!term_enable);
+
+	/* Control the pulldowns on the SPS signals */
+	sps_enable_pd(term_enable);
+
+	/* Reenable the sps inputs after enabling the pulldowns */
+	if (term_enable)
+		sps_enable_inputs(!term_enable);
+	update_term_state(SPS_TERM, term_enable);
+}
+
+void board_s3_term(int term_enable)
+{
+	if (!board_needs_s3_term() || (!term_enable == !term_enabled))
+		return;
+	CPRINTS("%sable S3 signal terminations", term_enable ? "En" : "Dis");
+
+	ap_tx_term_enable(term_enable);
+
+	if (!board_tpm_uses_i2c())
+		sps_term_enable(term_enable);
+}
+
+static int command_s3term(int argc, char **argv)
+{
+	ccprintf("Terminations:%s%s\n",
+		term_enabled & AP_TX_TERM ? " AP" : "",
+		term_enabled & SPS_TERM ? " SPS" : "");
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(s3term, command_s3term, "",
+			"Get the state of the S3 termination signals");
diff --git a/board/cr50/scratch_reg1.h b/board/cr50/scratch_reg1.h
index 4462212941..8802a9f5c5 100644
--- a/board/cr50/scratch_reg1.h
+++ b/board/cr50/scratch_reg1.h
@@ -49,12 +49,15 @@
 #define BOARD_DEEP_SLEEP_DISABLED    (1 << 13)
 /* Use Cr50_RX_AP_TX to determine if the AP is off or on */
 #define BOARD_DETECT_AP_WITH_UART    (1 << 14)
+/* Add terminations to signals in S3 */
+#define BOARD_NEEDS_S3_TERM          (1 << 15)
 /*
  * Macro to capture all properties related to board strapping pins. This must be
  * updated if additional strap related properties are added.
  */
 #define BOARD_ALL_PROPERTIES (BOARD_SLAVE_CONFIG_SPI | BOARD_SLAVE_CONFIG_I2C \
 	| BOARD_NEEDS_SYS_RST_PULL_UP | BOARD_USE_PLT_RESET | \
-	BOARD_DEEP_SLEEP_DISABLED | BOARD_DETECT_AP_WITH_UART)
+	BOARD_DEEP_SLEEP_DISABLED | BOARD_DETECT_AP_WITH_UART | \
+	BOARD_NEEDS_S3_TERM)
 
 #endif  /* ! __EC_BOARD_CR50_SCRATCH_REG1_H */